test-strip-narrow: adjust bundle removal for Windows test stability
MSYS was mangling $TESTTMP to C:\\Users\\...\\test-narrow-strip.t-flat/, which
caused `rm` to fail. The -f was suppressing -ENOENT, so the only clue something
was wrong was when 2 bundles were applied via `hg unbundle` on line 91, instead
of just 1. This changed the text output of `hg unbundle`.
The first `rm` wasn't causing an issue, but is changed for consistency with the
rest of the file.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}