ci: run release job steps under bash

Default shell was sh (dash), which lacks `set -o pipefail`; pin shell: bash.

.gitea/workflows/release.yml

@@ -10,6 +10,9 @@ jobs:
     runs-on: ubuntu-latest
     container:
       image: node:20-bookworm-slim
+    defaults:
+      run:
+        shell: bash
     steps:
       - name: Checkout
         uses: actions/checkout@v4