Fonts API: Replace _doing_it_wrong() with wp_trigger_error() in WP_Font_Face

[mohamedahamed]

In WP_Font_Face::validate_font_face_declarations(), _doing_it_wrong() is currently used to trigger notices when invalid font face properties are encountered (e.g., invalid font-family, src, or font-weight).

Above each of these four occurrences is an inline comment:
// @todo replace with wp_trigger_error().

Since wp_trigger_error() was introduced in 6.4.0 (the same version WP_Font_Face was introduced), we can now safely replace these calls to resolve the @todos.

This ticket updates the four instances in src/wp-includes/fonts/class-wp-font-face.php to use wp_trigger_error() instead of _doing_it_wrong().

*I will attach a Pull Request that addresses this issue shortly.*

This PR replaces the four instances of _doing_it_wrong() in WP_Font_Face::validate_font_face_declarations() with wp_trigger_error().

This resolves the inline @todo comments. Since wp_trigger_error() was introduced in WordPress 6.4.0 alongside the Fonts API, it is the preferred, modernized approach for triggering developer notices in core.

Trac ticket: https://core.trac.wordpress.org/ticket/65475

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