fix: remove invalid 'members: read' permission from registration workflow

The 'members' key is not a valid GitHub Actions permission scope, causing all
push-triggered workflow runs to fail with 'workflow file issue'. The org member
API calls in this workflow already have a try/catch fallback.

Author: GitHub Workshop Bot

.github/workflows/registration.yml

@@ -8,7 +8,6 @@ on:
 permissions:
   contents: write
   issues: write
-  members: read
 
 jobs:
   welcome: