tests/test-revlog-raw.py.out

extensions: remove superfluous pycompat.ispy3 check

This is always True now.

Differential Revision: https://phab.mercurial-scm.org/D12297

local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed
slicing test passed
issnapshot test passed
findsnapshot test passed