fix(action): should take default branch name as the version in CI (python#730)

Author: mattwang44

.github/workflows/ci.yml

@@ -13,4 +13,4 @@ jobs:
         run: sudo apt-get install gettext
 
       - name: Validate
-        run: VERSION=${{ github.event.pull_request.base.ref }} MODE=dummy make all
+        run: VERSION=${{ github.event.repository.default_branch }} MODE=dummy make all