github ci: don't create PR by default

Don't create the PR for the bump by the action itself. This will not run
CI checks.

Instead, opt for manual creation by default.

Signed-off-by: David Bauer <mail@david-bauer.net>

.github/workflows/bump-gluon.yml

@@ -18,7 +18,7 @@ on:
         description: "Skip pull request creation"
         type: boolean
         required: true
-        default: false
+        default: true
 
 jobs:
   update-gluon: