Fix ShopifyCLI::Theme::DevServer::CdnFonts class to support any font

[karreiro]

WHY are these changes introduced?

The #1821 PR fixes the font issue for the Assistant font, but other fonts were failing because of the ShopifyCLI::Theme::DevServer::CdnFonts regex as miss including the /assistant suffix.

WHAT is this pull request doing?

Now, the regex does not include the Assistant font suffix anymore.

How to test your changes?

1. Go to the theme directory
2. Update the config/settings_data.json file with a different font (e.g., fira_sans_n9)
3. Run shopify theme serve service
4. Open the http://127.0.0.1:9292
5. Check the fonts are now loading as expected

Post-release steps

None.

Update checklist

• I've added a CHANGELOG entry for this PR (if the change is public-facing)
• I've considered possible cross-platform impacts (Mac, Linux, Windows).
• I've left the version number as is (we'll handle incrementing this when releasing).
• I've included any post-release steps in the section above.

[macournoyer]

🔥