Add table grid needs styling update

[mateuszzagorski]

📝 Provide detailed reproduction steps (if any)

1. After bumping the editor to the latest version ("^35.2.0") build GH Writer.
2. Try to add a new table

✔️ Expected result

❌ Actual result

https://user-images.githubusercontent.com/11699569/195015955-1f633422-ac24-4eb2-80c0-b72327902d87.mov

❓ Possible solution

For the dark theme both the .ck-insert-table-dropdown-grid-box and .ck-insert-table-dropdown__label classes styles have to be updated.

📃 Other details

It is vital to check other themes (at least single theme light/dark default as well as the Sync with system theme mode)

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[mmotyczynska]

Might be a result of changing table grid items to ButtonView instances ckeditor/ckeditor5#12439.