Revert "[CI][Github] Disable premerge workflow on main"

This reverts commit 106f105.

Everything should be in working order now that the container job has been
updated to work properly. This has been tested on an individual job.

Author: boomanaiden154

.github/workflows/premerge.yaml

@@ -7,6 +7,9 @@ on:
   pull_request:
     paths:
       - .github/workflows/premerge.yaml
+  push:
+    branches:
+      - 'main'
 
 jobs:
   premerge-checks-linux: