[clanup] Remove pywikibot.QuitKeyboardInterrupt deprecated for 6 years
[clanup] Remove pywikibot.QuitKeyboardInterrupt deprecated for 6 years

also do not publish private _QuitKeyboardInterrupt class

Change-Id: I6f04b5f4664cd99477fb3579f3cf5bc0adc6ef24

wikimedia/pywikibot-core,wikimedia/pywikibot-core