tests: fix test-prune.t breakage
test-prune.t was broken due to 91d28bd0e04e in upstream Mercurial, which made
hidden commits visible when a local tag made the commit reachable. The fix is to
delete the tag in the test.
'''enable experimental obsolescence feature of Mercurial
OBSOLESCENCE IS AN EXPERIMENTAL FEATURE MAKE SURE YOU UNDERSTOOD THE INVOLVED
CONCEPT BEFORE USING IT.
/!\ THIS EXTENSION IS INTENDED FOR SERVER SIDE ONLY USAGE /!\
For client side usages it is recommended to use the evolve extension for
improved user interface.'''
import mercurial.obsolete
mercurial.obsolete._enabled = True