Try hdiutil detach

Author: sdmytrievs

.github/workflows/deploy-macos2.yml

@@ -71,6 +71,7 @@ jobs:
           cp -r "${{ github.workspace }}/Resources" "${{ github.workspace }}/${{ steps.strings.outputs.deploy-name }}/gem-selektor.app/Contents"
           cp "${{ github.workspace }}/Resources/rungems3-mac.sh" "${{ github.workspace }}/${{ steps.strings.outputs.deploy-name }}/rungems3.sh"
           cp "${{ github.workspace }}/Resources/README-macos.txt" "${{ github.workspace }}/${{ steps.strings.outputs.deploy-name }}/README.txt"
+          hdiutil detach "macos-${{ steps.strings.outputs.deploy-name }}" -force
 
       # Create ZIP archive for GitHub release (unchanged)
       - name: Create dmg