Add notes to clarify separate GCP steps for syncing library metadata

Author: prestoncabe

.github/workflows/load-library-metadata.yml

@@ -26,7 +26,8 @@ jobs:
         with:
           python-version: "3.11"
 
-      - name: Create GCP credentials file
+      # use a specific service account for sync script
+      - name: Create GCP credentials file (for sync script)
         run: |
           echo '${{ secrets.GCP_SERVICE_ACCOUNT_KEY }}' > bin/library/gcp-key.json
 
@@ -41,7 +42,8 @@ jobs:
       - name: Cleanup credentials
         run: rm bin/library/gcp-key.json
 
-      - name: Authenticate to Google Cloud
+      # Use a different service account with permissions to restart builder-api
+      - name: Authenticate to Google Cloud (for restarting builder-api)
         uses: google-github-actions/auth@v2
         with:
           workload_identity_provider: ${{ env.WORKLOAD_IDENTITY_PROVIDER }}