tests/test-revlog-raw.py.out

shortest: fix an off-by-1 when disambiguating against revnums

Revision "5" is an unambiguous hex prefix in a repo with 5 revisions;
it's only "4" and lower that are ambiguous.

Differential Revision: https://phab.mercurial-scm.org/D4420

local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed