dockerized_execution.py: drop stale reference-clones mention in comment

Reference clones are being removed from 2.5.0 entirely, so the
comment no longer applies.

Jira: CMK-33523
Change-Id: I439021edd81bd7e8c1b8c4651453840d55749e5e

Author: Synss

tests/testlib/script_helpers/dockerized_execution.py

@@ -508,7 +508,7 @@ def _git_repos() -> Mapping[str, DockerBind]:
     checkout_dir = repo_path()
     return {
         **{
-            # This ensures that we can also work with git-worktrees and reference clones.
+            # This ensures that we can also work with git-worktrees.
             # For this, the original git repository needs to be mapped into the container as well.
             path: DockerBind(bind=path, mode="ro")
             for path in git_essential_directories(checkout_dir)