Run flake update only on qgis repo

.github/workflows/flake-update.yml

@@ -13,7 +13,7 @@ jobs:
       # Give the default GITHUB_TOKEN write permission to commit and push the
       # added or changed files to the repository.
       contents: write
-
+    if: github.repository_owner == 'qgis'
     steps:
       - name: Check out repository
         uses: actions/checkout@v4