Do not run coveralls for non-development branches

It fails with 422 Unprocessable Entity

Author: horazont

.github/workflows/main.yaml

@@ -86,6 +86,7 @@ jobs:
         run: |
           set -euo pipefail
           coveralls
+        if: github.ref == 'refs/heads/devel' || github.event.pull_request.base.ref == 'devel'
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           COVERALLS_FLAG_NAME: python-${{ matrix.python-version }}
@@ -104,5 +105,6 @@ jobs:
         set -euo pipefail
         pip install coveralls
         coveralls --finish
+      if: github.ref == 'refs/heads/devel' || github.event.pull_request.base.ref == 'devel'
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}