CI: make sure that all [.yml] files [.gitlab] are terminated by newline

Context

Small clean up.

find .gitlab -type f -print0 | xargs -0 -L1 bash -c 'test "$(tail -c 1 "$0")" && echo "$0"' | while read -r f; do { cat $f; echo "" } > $f.bak; mv -v $f.bak $f; done

Manually testing the MR

Not sure.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR