Fix permissions for release artifacts

https://github.com/svenstaro/upload-release-action?tab=readme-ov-file#permissions

Author: microbit-matt-hillsdon

.github/workflows/release.yml

@@ -7,7 +7,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     permissions:
-      contents: read
+      contents: write
     steps:
       - uses: actions/checkout@v4
         with: