[llvm-mca] Make sure not to end the test files with an empty line.
It's super irritating.
[properly configured] git client then complains about that double-newline,
and you have to use --force to ignore the warning, since even if you
fix it manually, it will be reintroduced the very next runtime :/
Reviewers: RKSimon, andreadb, courbet, craig.topper, javed.absar, gbedwell
Reviewed By: gbedwell
Subscribers: javed.absar, tschuett, gbedwell, llvm-commits
Differential Revision: https://reviews.llvm.org/D47697