fix: hide font family option from newsletter

[laurelfulford]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

WordPress 7.0 introduces an Appearance > Fonts page. While this is somewhat redundant to the font options in the Newspack theme, it has a couple nice benefits:

• It can be used to upload font files, which then preview in the editor. We previously did this by SFTPing fonts and using Custom CSS, which doesn't preview in the editor.
• It adds an option to change the font face on a per-block basis, which can be nice.

There's some risks but on the whole it seems like a net positive... one issue is that the font family absolutely will not work in the Newsletter, so this PR removes it. It also renames an editor function to capture that it's now doing more than changing the layout width.

Closes NEWS-1625

How to test the changes in this Pull Request:

1. On a site running the latest WordPress RC, navigate to Appearance > Fonts.
2. Click Install Fonts, allow Google Fonts, pick at least one font and install a variant by checking at least one weight/style, and clicking 'Install':

3. Go to a regular post/page, and add a block like a paragraph or heading. When the block is selected, click the kebab (... menu next to the Typography header in the sidebar, and confirm one of the options you can add to the panel is 'Font':

4. Apply this PR.
5. Repeat step 3 with a post/page and confirm you can still add a 'Font' option via the Typography panel to change the font face.
6. Repeat step 3 with a newsletter post and confirm you CAN'T add a 'Font' option via the Typography panel -- it shouldn't show up as an option at all.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[Copilot]

Pull request overview

This PR updates the newsletter (email) block editor settings to remove the block-level font family control, since fonts registered in WordPress (including via Appearance > Fonts in WP 7.0) can’t be reliably rendered in email clients.

Changes:

• Clears __experimentalFeatures.typography.fontFamilies for newsletter/email editor contexts to hide the font family picker.

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[laurelfulford]

Thanks!!

[github-actions]

Hey @laurelfulford, good job getting this PR merged! 🎉

Now, the needs-changelog label has been added to it.

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