Fix release workflow

Bring back checkout before relase, looks like it
was removed by mistake in #49.

.github/workflows/release.yml

@@ -62,6 +62,7 @@ jobs:
     needs: build
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/checkout@v3
       - uses: oxidize-rb/actions/setup-ruby-and-rust@main
         with:
           ruby-version: "3.1"