Add newline for changelog CI job

Add newline for changelog CI job

In case the changelog file doesn't have an empty line at the end of the
file, the job may fail with the following error:

WARNING: Bullet list ends without a blank line; unexpected unindent.

This typically happens in MRs targeting the -S edition, as those
changelogs usually don't have an empty newline. This change ensures the
changelog job can pass and verify the title/desc contents even in those
cases.