Fix generating changelog for MRs and matchers with multiple matching labels

Previously we were checking if the matchers' labels in the changelog.yaml were all matching the labels of the MR.

This led to a matcher with tooling::pipelines and tooling::maintanence not to match since no MR would have both labels.

This change picks the matcher that best matches the labels of the MR without forcing all of the labels of the matcher to be included in the process.

Testing

Run:

 /path/to/gitlab-changelog -project-id 250833 \
                -release v13.3.0 \
                -starting-point-matcher "v13.2.0-rc1" \
                -config-file .gitlab/changelog.yml \
                -changelog-file CHANGELOG.md

And check that the MRs in the changelog are in the proper category.

Closes #3 (closed)