tests: drop the trailing exclamation point from some Windows abort messages
This likely goes with 95c4cca641f6.
Differential Revision: https://phab.mercurial-scm.org/D9537
#require rustfmt test-repo
$ . "$TESTDIR/helpers-testrepo.sh"
$ cd "$TESTDIR"/..
$ RUSTFMT=$(rustup which --toolchain nightly-2020-10-04 rustfmt)
$ for f in `testrepohg files 'glob:**/*.rs'` ; do
> $RUSTFMT --check --edition=2018 --unstable-features --color=never $f
> done