Disable rebase button in this project?

Hi. I opened a merge request for this project and later pushed the 'rebase' button in the web interface, to update the merge request to latest master. However this leads to a missing gpg signature failure in CI. How about disabling that button to avoid wasted CI cycles and contributor confusion? As far as I can tell, contributors needs to force-push their merge request branch to rebase things.

Failed job: https://salsa.debian.org/jas/pipeline/-/jobs/8111057

Checking that contributors have signed git commits following to CONTRIBUTING.md ..
$ SIGNING_KEY="$(git log --pretty="%GK" HEAD~1..HEAD)"
$ if [ -z "$SIGNING_KEY" ]; then echo "ERROR: Git commit message signature missing!" && exit 1; fi
ERROR: Git commit message signature missing!