WSGI wrapper: avoid forcing GC full collection by default

Still depends on the final name of the core setting.
see https://phab.mercurial-scm.org/D11204
2 jobs for !64 with topic/stable/wsgi-gc-rate in 55 seconds (queued for 1 second)
latest detached
Status Name Job ID Coverage
  Main
passed tests-current #227423

00:00:42

100.0%
 
  Compat
passed check-sdist #227424

00:00:55