[cleanup] cleanup scripts/delete.py
[cleanup] cleanup scripts/delete.py

- use str.format(...) instead of modulo for type specifier
  arguments.
- use single quotes for string literals
- remove preleading "u" from strings

Change-Id: If1bf2491274705f33a0a156fd39367205cff0e98

PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core,wikimedia/pywikibot-core