Add checkout to publish job for gh release create

gh release create requires a git repo to determine the repository
context even without --generate-notes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kesmit13

.github/workflows/publish.yml

@@ -172,6 +172,8 @@ jobs:
       url: https://pypi.org/p/singlestoredb
 
     steps:
+      - uses: actions/checkout@v3
+
       - name: Download Linux wheels and sdist
         uses: actions/download-artifact@v4
         with: