Revert changes

Author: KianW-DfE

.github/workflows/build.yml

@@ -73,7 +73,7 @@ jobs:
           path: TestResults/Merged/SummaryGithub.md
 
       - name: Log in to GHCR
-#        if: ${{ github.event_name == 'push' }}
+        if: ${{ github.event_name == 'push' }}
         uses: docker/login-action@v4
         with:
           registry: ghcr.io
@@ -102,7 +102,7 @@ jobs:
           context: .
           file: src/SchoolAccount.Web.Mvc/Dockerfile
           target: final
-          push: true
+          push: ${{ github.ref == env.MAIN_BRANCH }}
           tags: ${{ steps.meta.outputs.tags }}
 
       - name: Publish