[cleanup] cleanup scripts/script_wui.py
[cleanup] cleanup scripts/script_wui.py

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

Change-Id: I02acc2b1c95b8c3f43afe6e92e42059febf00796

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