fix JME matching test

ATM, this MR only reverts commit 6c79a438 (!169 (merged)), as it breaks the JME matching test (which couldn't be spotted, since we had skipped the CI). Here is the output of the failing test:

----------------------------------------------------------                                                                                   
1/19 Testing: JEC_JMEmatching                                                                                                                                                                                                                                                             
1/19 Test: JEC_JMEmatching                                                                                                                   
Command: "/home/connorpa/Exercises/DasAnalysisSystem/Core.build/JEC/JEC_JMEmatching"                                                         
Directory: /home/connorpa/Exercises/DasAnalysisSystem/Core.build/JEC                                                                         
"JEC_JMEmatching" start time: Jul 16 23:12 CEST                                                                                                                                                                                                                                           
Output:                                                               
----------------------------------------------------------                                                                                   
Running 1 test case...                                                                                                                       
matched:                                                                                                                                     
(2483.14,0.321438,-0.196805,106.613)    (2524.79,0.327749,-0.195445,58.0793)                                                                 
(39.1258,-0.116546,0.146107,8.07695)    (33.5166,-0.122238,0.161481,7.07595)                                                                 
(40.0953,-2.04749,1.90519,8.54279)      (34.4065,-2.00748,1.9085,6.99561)                                                                    
fake jets:                                                                                                                                   
(2134.21,-0.942423,2.9649,89.2931)                                    
(26.8832,-3.20082,0.185538,4.90555)                                                                                                          
(17.3033,-4.66682,0.165994,4.10577)                                   
(16.6046,0.366067,-0.827474,4.87341)                                                                                                                                                                                                                                                      
(16.549,-2.6873,2.45095,3.45013)                                                                                                             
(12.3946,-1.59309,1.73679,2.57709)                                                                                                           
(12.211,1.56773,2.39476,3.73802)                        
(11.8022,3.97949,3.13835,3.05636)                                                                                                            
(11.4237,-4.25829,2.96043,2.93494)                                                                                                           
(11.0795,-1.12393,-1.40509,2.68032)                                                                                                          
(10.027,-1.8964,-1.73484,2.41908)                                                                                                            
miss jets:                                                                                                                                   
(2540.75,-0.939323,2.96712,42.6797)                                                                                                          
(376.691,0.626885,0.162126,54.7152)                                                                                                          
(286.42,0.145464,-2.71124,30.6079)                                    
/home/connorpa/Exercises/DasAnalysisSystem/Core/JEC/test/JMEmatching.cc(61): error: in "matching": check matching.match_its.size() == 4 has failed [3 != 4]
/home/connorpa/Exercises/DasAnalysisSystem/Core/JEC/test/JMEmatching.cc(62): error: in "matching": check matching.fake_its.size() == 10 has failed [11 != 10]
/home/connorpa/Exercises/DasAnalysisSystem/Core/JEC/test/JMEmatching.cc(63): error: in "matching": check matching.miss_its.size() == 2 has failed [3 != 2]
*** 3 failures are detected in the test module "Matching"                                                         

I should have asked in !169 (merged) but how can this affect the application of JES corrections where no matching is needed?

JEC/interface/JMEmatching.h

@@ -81,7 +81,7 @@ template<typename RecContainer = std::vector<RecJet>,
                      matchedGen(nGen, false);
         match_its.reserve(min(nRec,nGen));
         while (!candidates.empty()) {
-            auto& [iRec, iGen] = candidates.top();
+            auto [iRec, iGen] = candidates.top();
             candidates.pop();
 
             // skip already matched objects