Fix TPU CI for non-forks (#14688)

Author: carmocca

.github/workflows/ci-circleci.yml

@@ -8,7 +8,10 @@ on:
       - "src/pytorch_lightning/**"
       - "tests/tests_pytorch/**"
       - "setup.cfg"  # includes pytest config
-  pull_request_target:
+  # should use `pull_request_target` but it's blocked by
+  # https://github.com/CircleCI-Public/trigger-circleci-pipeline-action/issues/27
+  # so this job will not run on forks until the above is fixed or we replace CircleCI for another provider
+  pull_request:
     branches: [master, "release/*"]
     paths:
       - ".github/workflows/ci-circleci.yml"
@@ -23,9 +26,6 @@ jobs:
   trigger-circleci:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-        with:
-          ref: ${{ github.event.pull_request.head.sha }}
       - uses: CircleCI-Public/[email protected]
         env:
           CCI_TOKEN: ${{ secrets.CCI_TOKEN }}