Collapse requests for the flang AIX buildbot (#363)

allow collapseRequests for flang AIX bot:
https://lab.llvm.org/buildbot/#/builders/201, due to a long build queue.
Most aix bots already allow collapseRequests so this would be consistent
with existing behaviour.

Author: madanial0

buildbot/osuosl/master/config/builders.py

@@ -2538,7 +2538,6 @@
 
     {'name' : 'ppc64-flang-aix',
     'tags'  : ["flang", "ppc", "ppc64", "aix"],
-    'collapseRequests' : False,
     'workernames' : ['ppc64-flang-aix-test'],
     'builddir': 'ppc64-flang-aix-build',
     'factory' : UnifiedTreeBuilder.getCmakeWithNinjaBuildFactory(