Twenty Twenty-Four: system-serif slug type-o

[RavanH]

Description

When trying the set, for example, the global headings font family to System Serif, the global style setting will be converted to style rule font-family: var(--wp--preset--font-family--system-Serif); (notice the upper case S) referencing a non-existent root variable.

Testing Instructions

1. Go to global style settings and change the Headings font face to System Serif.
2. Save styles.
3. Verify any headings on the front end: they will be using the browser default, not the root --wp--preset--font-family--system-serif (notice the lower case S) value.

Replaces upper case S in slug system-Serif by lower case s.

Trac ticket: https://core.trac.wordpress.org/ticket/60325

[onemaggie]

This change makes sense and it also makes theme.json consistent with the style variations. Thanks for the patch

[huzaifaalmesbah]

Nice catch! I followed your testing instructions and observed the issue as well. I agree, your patch seems effective and well-done.

Nice catch @RavanH.

[swissspidy]

In 57351:

Twenty Twenty-Four: Change font family slug to lowercase.

Ensures referencing the correct CSS custom property.

Props RavanH, poena, onemaggie, huzaifaalmesbah, mukesh27.
Fixes #60325.