Use new merge alias (label=X) for lhcb-test-throughput

lhcbnightlyconf/UpgradeTests.py

@@ -82,13 +82,7 @@ throughput.LCG.version = '96b'
 throughput.Gaudi.version = 'master'
 for p in throughput.projects:
     if p.name not in ('LCG', 'DBASE', 'PARAM'):
-        p.checkout_opts = {
-            'merges':
-            getMergeRequests(
-                p.name,
-                target_branch=p.version,
-                labels=['lhcb-test-throughput'])
-        }
+        p.checkout_opts['merges'] = ['label=lhcb-test-throughput']
 throughput.platforms = [
     'x86_64-centos7-gcc8-opt',
     'x86_64+avx2+fma-centos7-gcc8-opt',