Remove feature flag for LFS integrity check via quarantined objects

The change to use the quarantine environment for LFS integrity checks
has been enabled in production now for some time with the expected
benefits: if used, the new check is up to several magnitudes faster than
the old LFS pointer check.

Drop the feature flag and make this new feature generally available.

Changelog: added

changelogs/unreleased/pks-lfs-integrity-quarantine-remove-feature-flag.yml

+---
+title: Remove feature flag for LFS integrity check via quarantined objects
+merge_request: 59991
+author:
+type: performance

config/feature_flags/development/lfs_integrity_inspect_quarantined_objects.yml

----
-name: lfs_integrity_inspect_quarantined_objects
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/58634
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/327440
-milestone: '13.11'
-type: development
-group: group::gitaly
-default_enabled: false

lib/gitlab/gitaly_client/blob_service.rb

@@ -115,7 +115,7 @@ module Gitlab
         # necessary graph walk to detect only new LFS pointers and instead scan
         # through all quarantined objects.
         git_env = ::Gitlab::Git::HookEnv.all(@gitaly_repo.gl_repository)
-        if Feature.enabled?(:lfs_integrity_inspect_quarantined_objects, @project, default_enabled: :yaml) && git_env['GIT_OBJECT_DIRECTORY_RELATIVE'].present?
+        if git_env['GIT_OBJECT_DIRECTORY_RELATIVE'].present?
           repository = @gitaly_repo.dup
           repository.git_alternate_object_directories = Google::Protobuf::RepeatedField.new(:string)