fix: octal rule triggers on time format

[nicholasmhughes]

Time values such as this:

some_calendar_entry:
  file.managed:
    - name: /tmp/my_unit_file
    - contents: |
        OnCalendar=Sun 18:00

should not trigger this rule.

Changed the regex to accommodate this case while still catching/ignoring previous identified test cases

[nicholasmhughes]

@roaldnefs

[roaldnefs]

Thanks @nicholasmhughes for your contribution! Unfortunately it took a while before I could find time for a review. I've rebased the code, added the missing changelog entry and made a minor change in the code.