Revert "Do not create build requests for workers if offline longer th…

…an 30 minutes."

This reverts commit 618344c and
fab27e2.

Otherwise we observe the failure in presubmit:
   $ cd buildbot/osuosl/master && BUILDBOT_TEST=1 buildbot checkconfig
   Configuration Errors:
   Unknown BuildmasterConfig key ignoreOfflineWorkersTimeout

FWICT, ignoreOfflineWorkersTimeout is not documented anywhere. It has been
implied that LLVM's buildbot has downstream patches. I could not find where
these were published, and the issue is now blocking me from further updates to
CI. Rip everything out for now.

>> LLVM's buildbot seems to be deploying a forked version

Link: 618344c

buildbot/osuosl/master/master.cfg

@@ -39,9 +39,6 @@ c['workers'] = config.workers.get_all()
 
 c['protocols'] = {'pb': {'port': "tcp:9990:interface=127.0.0.1" if test_mode else 9990}}
 
-if not test_mode: # Config key only supported on downstream buildbot fork.
-  c['ignoreOfflineWorkersTimeout'] = 30 # minutes.
-
 ####### CHANGESOURCES
 
 ##from buildbot.changes.pb import PBChangeSource