ci: revert temporary pull_request trigger

We have verified the fix works. Reverting the temporary trigger before merge.

TAG=agy

CONV=acb0ee9b-3d87-4b9e-b3c6-0d4aa3efbd35

Author: suztomo

.github/workflows/regenerate-all.yml

@@ -4,7 +4,6 @@ on:
   push:
     branches:
       - main
-  pull_request:
 
 permissions:
   contents: read