Typography Support: Font family does not work in block styles in the site editor

[stacimc]

Description

In the site editor, if you attempt to modify the font-family of an individual block through the Typography panel in its Inspector Controls, the style is not visually reflected in the editor.

It looks like the class name is correctly added to the block, but no relevant styles are present in the stylesheet.

Font family styles selected through the Global Styles panel do work correctly. The issue is for blocks when edited individually through the site editor.

Step-by-step reproduction instructions

1. Activate a blocks theme like TT1-blocks.
2. Go to the site editor and insert a Site Title (or any other block that supports font-family, like Buttons or Navigation) into the header template.
3. Click on the block, open the Inspector Controls, and navigate to the Typography panel.
4. Make a selection from the font family control.
5. Observe that the style of the block does not visually change.
6. Inspect the block in the developer tools; you should see that the relevant font-family class has been added (for example has-geneva-verdana-font-family), but there are no styles present for the class.

Screenshots, screen recording, code snippet

Environment info

No response

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes