Stop referencing GCS_CREDENTIALS (#4624)

We now use git to download recordings.

(cherry picked from commit e2eb519)

Author: pquentin

.github/workflows/validate-pr.yml

@@ -61,8 +61,6 @@ jobs:
           fi
           node scripts/upload-recording/download.js --branch $branch --git
           node scripts/clone-elasticsearch/index.js --branch $branch
-        env:
-          GCS_CREDENTIALS: ${{ secrets.GCS_CREDENTIALS }}
 
       - name: Run validation
         id: validation