Remove stray temporary release notes file
Remove stray temporary release notes file

m1.md was incorporated into the correct final release version file but
for some reason the temporary file wasn't deleted.

ponylang/ponyc,jemc/ponyc,ponylang/ponyc,jemc/ponyc,ponylang/ponyc,dipinhora/ponyc,dipinhora/ponyc,dipinhora/ponyc,jemc/ponyc