[cleanup] cleanup scripts/illustrate_wikidata.py
[cleanup] cleanup scripts/illustrate_wikidata.py

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

Change-Id: I0bffc9d7ef2061921bec86e789e545b3e114652e

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