[cleanup] clean scripts/reflinks.py
[cleanup] clean scripts/reflinks.py

- remove preleading "u" from strings
- use single quotes for string literals and double quotes
  **only** if they consist of single quotes within them
- use str.format(...) instead of modulo for type specifier
  arguments
- use "+" to concatenate strings in some cases

Change-Id: I04354e9c14c16dcc713a62d841314dd9d911330a

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