Disable certain actions from running on forks (#23747)

* Disable certain actions from running on forks

* Address some feedback

* Check for forks in build-docker job

.github/workflows/docker-push-mirrored.yml

@@ -10,6 +10,7 @@ on:
 jobs:
   build-docker:
     name: cd/Push mirrored docker images
+    if: github.repository_owner == 'mattermost'
     runs-on: ubuntu-22.04
     steps:
       - name: Checkout mattermost project