CI: Do not fail the build if Coveralls fails

We had many build failures with "oh, the code coverage was not sent to that service", which is a little "them problem" rather than an "us problem", so I configured this to not be a failure.

Author: olleolleolle

.github/workflows/ruby.yml

@@ -43,6 +43,7 @@ jobs:
         RAILS_ENV: test
       run: bundle exec rake spec
     - name: Report to Coveralls
+      continue-on-error: true # Don't fail the build if Coveralls fails to upload.
       uses: coverallsapp/github-action@v2
       with:
         github-token: ${{ secrets.github_token }}