ResizeTooltip: Use default.fontFamily on tooltip

[richtabor]

What?

Small PR to fix one of the issues reported as part of #48443.

Why?

The theme's body font family is incorrectly applied to the resize tooltip. The editor's UI should not be influenced by the theme's font family.

How?

Use ${ font( 'default.fontFamily' ) }; on resize tooltip styles.

Testing Instructions

1. Switch to a theme using a noticeable body font (like Twenty Fifteen).
2. Open a Post or Page.
3. Insert a Spacer block.
4. Resize it using the ResizableBox handle.
5. See the resize tooltip no longer using the body font from the theme.

Screenshots or screencast

Before:

After:

[github-actions]

Flaky tests detected in 1f8a5ef.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/4347833358
📝 Reported issues:

• [Flaky Test] should navigate block hierarchy using only the keyboard #47640 in specs/editor/various/block-hierarchy-navigation.test.js
• [Flaky Test] should navigate using the list view sidebar #47001 in specs/editor/various/block-hierarchy-navigation.test.js

[ciampo]

Thank you for working on this 🚀

Before merging, could you add an entry to the CHANGELOG ?

[mtias]

Thanks! This has been bothering me quite a bit :)