[skip ci] Update release workflow

Author: kateinoigakukun

CONTRIBUTING.md

@@ -112,7 +112,7 @@ $ git push origin 0.6.0
 # After GitHub Actions "Build gems" is done
 # https://github.com/ruby/ruby.wasm/actions/workflows/build-gems.yml
 $ gh run download <run-id>
-$ for pkg in cross-gem/pkg/ruby_wasm-*; do gem push $pkg; done
+$ for pkg in cross-gem-*/ruby_wasm-*; do gem push $pkg; done
 $ gem build && gem push ruby_wasm-*.gem && rm ruby_wasm-*.gem
 $ (cd packages/gems/js/ && gem build && gem push js-*.gem && rm js-*.gem)
 $ rake bump_dev_version