pywikibot: Fix KeyError in create_warnings_list
pywikibot: Fix KeyError in create_warnings_list

create_warnings_list() was looking for an offset entry in the passed-in
response dict which is (no longer?) being set for that code path. This
patch uses the _offest argument to upload() instead.

Bug: T301610
Change-Id: Ibe63befb6f80a0831adee446c66c4fb875ff0b1d

wikimedia/pywikibot-core,wikimedia/pywikibot-core