Revert "[bugfix] Fix updating pip on AppVeyor"
Revert "[bugfix] Fix updating pip on AppVeyor"

This reverts commit 2af76c19ef1c22f0ccff365c7b804656207acc6d.

Change-Id: Ib510a42ccccb1a6d53b91fb8f6939257f3ef93f9

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