Autotag using a PAT instead of github.token

Using github.token means that the action will not trigger any further
workflows. However, what we want is for workflows to be triggered. So we
use a PAT here to ensure that happens.

This is secure since PRs only have access to secrets if the PR is made
from a branch within the same repository.

.github/workflows/tests.yml

@@ -57,7 +57,7 @@ jobs:
       pull-requests: write
     env:
       PR: ${{ github.event.pull_request.number }}
-      GH_TOKEN: ${{ github.token }}
+      GH_TOKEN: ${{ secrets.LABEL_API_TOKEN }}
     steps:
       - uses: actions/checkout@v4
       - name: Add the pr-pull label to the issue