FIX: Do not allow_any on fonts site_settings (#30780)

Both heading_font and body_font should not allow
additional user-defined values, these are lists with
predefined choices. The UI already prevents this
because the font selector dropdown is unique, but
we want to make sure the setting definition reflects
this too.

lib/site_settings/type_supervisor.rb

@@ -269,7 +269,11 @@ class SiteSettings::TypeSupervisor
     if type == self.class.types[:list] || type == self.class.types[:string]
       if @allow_any.key?(name) && !@allow_any[name]
         split = val.to_s.split("|")
-        diff = (split - @choices[name])
+        resolved_choices = @choices[name]
+        if resolved_choices.first.is_a?(Hash)
+          resolved_choices = resolved_choices.map { |c| c[:value] }
+        end
+        diff = (split - resolved_choices)
         if diff.length > 0
           raise Discourse::InvalidParameters.new(
                   I18n.t(