ci: enable RBE testing for all PRs on the main fork

.github/workflows/ci.yaml

@@ -54,7 +54,7 @@ jobs:
               run: echo "config=rbe" >> $GITHUB_OUTPUT
               # Only run on main branch (or PR branches that contain 'rbe') to reduce the matrix size for PRs
               # Don't run RBE if there are no EngFlow creds which is the case on forks
-              if: (github.ref == 'refs/heads/main' || contains(github.head_ref, 'rbe')) && env.ENGFLOW_PRIVATE_KEY != ''
+              if: env.ENGFLOW_PRIVATE_KEY != ''
         outputs:
             # Will look like ["local", "rbe"]
             config: ${{ toJSON(steps.*.outputs.config) }}