Put back main branch for staging (#34)

Co-authored-by: Nena <nena@edgeandnode.com>

Author: nenadjaja

.github/workflows/ci-cd-staging.yml

@@ -3,7 +3,7 @@ name: Staging CI/CD
 on:
   push:
     branches:
-      - develop
+      - main
 
 env:
   BASE_IMAGE: ghcr.io/graphprotocol/graph-docs-staging