fix: update server_url reference to use vars in release workflow

.gitea/workflows/release.yml

@@ -57,7 +57,7 @@ jobs:
       - name: Create Release
         uses: akkuman/gitea-release-action@v1
         with:
-          server_url: ${{ SERVER_URL }}
+          server_url: ${{ vars.SERVER_URL }}
           tag_name: ${{ steps.changelog.outputs.version }}
           name: "Release ${{ steps.changelog.outputs.version }}"
           body: ${{ steps.changelog.outputs.description }}