Fix focus outline of block items in blocks menu

[josephfusco]

These changes clean up the outline styles for the blocks menu.

Fixes #53600

Demo of Proposed Changes

gutenberg-53600-solution.mov

[github-actions]

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[github-actions]

👋 Thanks for your first Pull Request and for helping build the future of Gutenberg and WordPress, @josephfusco! In case you missed it, we'd love to have you join us in our Slack community, where we hold regularly weekly meetings open to anyone to coordinate with each other.

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[josephfusco]

Hey @ajitbohra, thank you for taking a look at these changes!

The CSS proposed in this PR is causing some tests to fail. What can I do to help clear these?