fix newline in git log format

[kpedro88]

Addresses issue reported at #125 (comment) / cms-sw/cmssw#43592 (comment). Proof that it works as expected now: kpedro88/cmssw@aac6c7d

[cmsbuild]

A new Pull Request was created by @kpedro88 (Kevin Pedro) for branch master.

@cmsbuild, @aandvalenzuela, @smuzaffar, @iarspider can you please review it and eventually sign? Thanks.
@rappoccio, @sextonkennedy, @antoniovilela you are the release manager for this.
cms-bot commands are listed here

[cmsbuild]

cms-bot internal usage

[smuzaffar]

+externals

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs after it passes the integration tests. This pull request will now be reviewed by the release team before it's merged. @sextonkennedy, @rappoccio, @antoniovilela (and backports should be raised in the release meeting by the corresponding L2)