style: Fix serialization of the font-variant shorthand when font-variant-emoji is preffed off

Depends on D160256

Differential Revision: https://phabricator.services.mozilla.com/D160257

components/style/properties/shorthands/font.mako.rs

@@ -418,6 +418,13 @@
                    nb_normals += 1;
                 }
             }
+        % if prop == "emoji":
+            else {
+                // The property was disabled, so we count it as 'normal' for the purpose
+                // of deciding how the shorthand can be serialized.
+                nb_normals += 1;
+            }
+        % endif
         % endfor