[bugfix] endprefix parameter not working in Category.articles()
[bugfix] endprefix parameter not working in Category.articles()

The endprefix parameter should be used to set the value of
gcmendsortkeyprefix, rather than cmendsortkeyprefix.

Bug: T247201
Change-Id: Ieab2fa159d73e1e13656c9bc15470b4d5ba5ed55

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