release: remove automatic workflow trigger (#943)

Remove the trigger to automatically run the release workflow when
changes are merged to the release branch. This will give us better
control over our release process and allow us to make changes to the
branch if needed without running the workflow.

.github/workflows/release.yml

@@ -2,8 +2,6 @@ name: release
 
 on:
   workflow_dispatch:
-  push:
-    branches: [ release ]
 
 jobs:
 # ================================