[tests] Use Portalwiki for logentries_tests.py
[tests] Use Portalwiki for logentries_tests.py

btrfswiki is MW 1.19 which is no longer supported.
Remove btrfswiki from test matrix and replace it with
portalwiki which is 1.23

Bug: T268979
Change-Id: Ic4ca4e8f7f4693c66d1d641768000674203db263

wikimedia/pywikibot-core,wikimedia/pywikibot-core