Revert ".github/scripts/auto-backport.py: validate backport candidate with Fixes prefix"

This reverts commit 8414cd743e. It prevents
pulling pull requests that do have "Fixes" references.

.github/scripts/auto-backport.py

@@ -129,20 +129,6 @@ def backport(repo, pr, version, commits, backport_base_branch):
             logging.warning(f"GitCommandError: {e}")
 
 
-def with_github_keyword_prefix(repo, pr):
-    pattern = rf"(?:fix(?:|es|ed))\s*:?\s*(?:(?:(?:{repo.full_name})?#)|https://github\.com/{repo.full_name}/issues/)(\d+)"
-    match = re.findall(pattern, pr.body, re.IGNORECASE)
-    if not match:
-        print(f'No valid close reference for {pr.number}')
-        comment = f':warning:  @{pr.user.login} PR body does not contain a Fixes reference to an issue '
-        comment += ' and can not be backported\n\n'
-        comment += 'The following labels were removed:\n'
-        create_pr_comment_and_remove_label(pr, comment)
-        return False
-    else:
-        return True
-
-
 def main():
     args = parse_args()
     base_branch = args.base_branch.split('/')[2]
@@ -183,8 +169,6 @@ def main():
         if not backport_labels:
             print(f'no backport label: {pr.number}')
             continue
-        if args.commits and not with_github_keyword_prefix(repo, pr):
-            continue
         commits = get_pr_commits(repo, pr, stable_branch, start_commit)
         logging.info(f"Found PR #{pr.number} with commit {commits} and the following labels: {backport_labels}")
         for backport_label in backport_labels: