[Minor] ~bugfix Fix directory exploring in TrigCost CSV export

I found that trig cost CSV exporting only works for a single top-level directory.

ATR-22335 is a full reprocessing so had two - this showed up the bug.

Simple fix.

Trigger/TrigCost/TrigCostAnalysis/util/trigCostHistToCSV.cxx

@@ -114,8 +114,8 @@ void exploreTree(TFile* file, const size_t level = 0, std::vector<TString> dir =
         exploreTree(file, level + 1, dir);
       } else {
         exportDirectory(file, dir, walltime);
-        dir.pop_back();
       }
+      dir.pop_back();
     } else if (name.First("_walltime") != kNPOS) {
       // This is fine
     } else {