[cleanup] Remove deactivated code in cosmetic_changes.py
[cleanup] Remove deactivated code in cosmetic_changes.py

- remove deactivated code in cosmetic_changes.py but save it in T57185
- use textlib.NON_LATIN_DIGITS for fa-digits
- use string.format() in favour of modula operator
- return text in commonsfiledesc due to PEP 8

Change-Id: I04c725b3cb93bfcba3c1576eb5775ca359c25e78

wikimedia/pywikibot-core,wikimedia/pywikibot-core