📝 Provide detailed reproduction steps (if any)

1. Use https://ckeditor.com/ckeditor-5/builder/
2. Choose fx. "Inline Editor"
3. Add ShowBlocks plugin
4. Click showBlocks in toolbar

✔️ Expected result

Icons should be rendered.

❌ Actual result

Only borders are rendered.

❓ Possible solution

Styles for the icons are not compatible with these editors.

📃 Other details

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