ci : add zip extension to xcframework artifact name (#3120)

This commit add the .zip extension to the xcframework artifact name in
the GitHub Actions workflow.

The motivation for this that the release job will look for .zip files
and will not find the xcframework artifact without the extension, and
hence will not upload it to the release.

.github/workflows/build.yml

@@ -964,7 +964,7 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           path: whisper-${{ needs.determine-tag.outputs.tag_name }}-xcframework.zip
-          name: whisper-${{ needs.determine-tag.outputs.tag_name }}-xcframework
+          name: whisper-${{ needs.determine-tag.outputs.tag_name }}-xcframework.zip
 
   android:
     if: ${{ github.event_name == 'push' || github.event_name == 'pull_request' ||