Github Actions: commitbot runs conditionally on boostorg/boost repo (#916)

.github/workflows/commit-bot.yml

@@ -13,6 +13,7 @@ jobs:
   update-modules:
     runs-on: ubuntu-latest
     name: Commit Bot
+    if: github.repository == 'boostorg/boost'
 
     steps:
       - name: Check for module updates