PYTHON-5047 Do not run nightly release check on forks (#2134)

(cherry picked from commit a641337)

Author: blink1073

.github/workflows/release-python.yml

@@ -37,6 +37,7 @@ jobs:
   pre-publish:
     environment: release
     runs-on: ubuntu-latest
+    if: github.repository_owner == 'mongodb' || github.event_name == 'workflow_dispatch'
     permissions:
       id-token: write
       contents: write