ci: do not run commitlint GitHub Action on dependabot PRs

Currently commitlint is only skipped for PR at the time dependabot
creates them. Once Mergify rebases them, commitlint is started anyway.
This causes failed CI runs, which then need to be ignored. It is cleaner
to not run commitlint on any PR that dependabot owns.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

.github/workflows/commitlint.yaml

@@ -11,7 +11,7 @@ permissions:
 jobs:
   commitlint:
     name: commitlint
-    if: ${{ github.actor != 'dependabot[bot]' }}
+    if: ${{ github.event.pull_request.user.login != 'dependabot[bot]' }}
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3