[cleanup] cleanup scripts/maintenance/make_i18n_dict.py
[cleanup] cleanup scripts/maintenance/make_i18n_dict.py

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

Change-Id: I5788e1117e5a888cd6b0303924a703561af6efed

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