fix: MCD-601: Remove unnecessary content_lock release before entity deletion

[petarbasic]

Summary

• Removes the content_lock lock-release code from cleanUpContent() before entity deletion
• In content_lock 2.x, hook_entity_predelete() blocked deletion of locked entities (via exit(0)), so releasing locks first was necessary
• In content_lock 3.x, this was replaced with hook_entity_access() for the delete operation, which $entity_storage->delete() does not invoke — so the lock release is no longer needed
• Locks are cleaned up automatically via hook_entity_delete() after deletion

Supersedes #32

Test plan

• Verify test cleanup works correctly with content_lock 3.x (tested via ldp-project CI)

[fago]

duplicate