Remove isolation test lock-stats

Remove isolation test lock-stats

This test is proving to be unstable in the CI for Windows, at least.
The origin of the issue is that the deadlock_timeout requests may not
be processed, causing the lock stats to not be updated.  This could be
mitigated by making the hardcoded sleep longer, however this would cost
in runtime on fast machines.  On slow machines, there is no guarantee
that an augmented sleep would be enough.

An isolation test may not be the best method to write this test
(TAP test with injection point with a NOTICE+wait_for_log before
processing the deadlock_timeout request should remove the need of a
sleep).  As we are late in the release cycle, I am removing the test for
now to keep the CI and the buildfarm a maximum stable.  Let's revisit
this part later.

Discussion: https://postgr.es/m/hlkdrplgrmudbspibsuq6xooxrqxqsgwo6x5b6x5ptvkgjbe7w@xogt6xgua6dz