Fix excessive-permissions

Xref https://docs.zizmor.sh/audits/#excessive-permissions

Author: weiji14

.github/workflows/pypi-release.yaml

@@ -13,6 +13,8 @@ on:
     branches:
       - main
 
+permissions: {}
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true