Add letter spacing inheritance for the navigation block

[graylaurenm]

What?

Adds inheritance of letter spacing for the navigation block.

Why?

The navigation block uses inherit definitions to support typography styles. The letter-spacing definition is missing.

How?

Adds the necessary line.

Testing Instructions

<!-- wp:navigation {"ref":60591,"style":{"typography":{"letterSpacing":"0.1em"}}} /-->

Testing Instructions for Keyboard

N/A

Screenshots or screencast

Before:

After:

[github-actions]

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[github-actions]

👋 Thanks for your first Pull Request and for helping build the future of Gutenberg and WordPress, @graylaurenm! In case you missed it, we'd love to have you join us in our Slack community.

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[talldan]

Thanks for the contribution @graylaurenm! The fix looks good to me.

For anyone testing, you have to set Submenus > 'Open on click' in the navigation block's settings to notice the bug. When you do that, letter spacing doesn't affect the submenu button.

[ellatrix]

I just cherry-picked this PR to the wp/6.6-rc-1 branch to get it included in the next release: 88002da