This reverts commit f825d70e25feae8cd9da84e768ec6075edbc2200.

 * Use `settings.delayed_group_deletion=False` as that is the
   recommended method to turn off the delayed group deletion now.
 * Change test to look for `default` as `pages` is not mentioned in
   the docs[1]

[1] https://docs.gitlab.com/ee/api/sidekiq_metrics.html#get-the-current-queue-metrics

test: attempt to make functional test startup more reliable

The functional tests have been erratic. Current theory is that we are
starting the tests before the GitLab container is fully up and
running.

  * Add checking of the Health Check[1] endpoints.
  * Add a 20 second delay after we believe it is up and running.
  * Increase timeout from 300 to 400 seconds

[1] https://docs.gitlab.com/ee/user/admin_area/monitoring/health_check.html

Use the GitLab docker image 15.2.0-ee.0 in the functional testing.

This reverts commit 67ab24fe5ae10a9f8cc9122b1a08848e8927635d.

Enable using GitLab Enterprise Edition (EE) in the functional tests.
This will allow us to add functional tests for EE only features in the
functional tests.