Don't fail sponsors tagging, since it's optional

Also, it's guaranteed to fail for PRs from forks since those can't access the required access token to perform the graphql queries required to determine sponsorships.

Author: kzu

.github/workflows/sponsor.yml

@@ -8,6 +8,7 @@ on:
 jobs:
   sponsor:
     runs-on: ubuntu-latest
+    continue-on-error: true
     env:
       token: ${{ secrets.GH_TOKEN }}
     if: ${{ !endsWith(github.event.sender.login, '[bot]') && !endsWith(github.event.sender.login, 'bot') }}