rules-repo config description incorrect

[Chris Johnston]

  rules-repo:
    type: string
    description: |
        Git repository with custom rules. Rules have to be in *.rules files

This would indicate that any file that doesn't end in .rules would be ignored. In reality, it appears that .rules, .yaml, and .yml files are all considered valid:

    for root, dirs, filenames in os.walk(PATHS["external_rules_path"]):
        for filename in filenames:
            # Ignore files such as .launchpad.yaml and .yamllint.yaml
            if filename.startswith("."):
                continue
            match = re.match("^.*\.(yaml|yml|rules)$", filename) # NOQA W605
            if match:
                # Wildcard filename part to allow rule files to disappear
                rule_files.append("{}/*.{}".format(root, match.group(1)))
    return sorted(list(set(rule_files))) # dedup entries