tests/histedit-helpers.sh

tests: fix deprecation warning about regex flags not at beginning of expr

This may only show up when running the tests under python3.6+. Currently the
only test that does this is test-patchbomb-tls.t, and it only uses (?i), so
that's all that's handled at the moment.

Differential Revision: https://phab.mercurial-scm.org/D7552

fixbundle() {
    grep -v 'saving bundle' | grep -v 'saved backup' | \
        grep -v added | grep -v adding | \
        grep -v "unable to find 'e' for patching" | \
        grep -v "e: No such file or directory" | \
    cat
}