style: Remove old warning allow which is no longer relevant.

-moz-appearance uses cbindgen since a long time ago.

Differential Revision: https://phabricator.services.mozilla.com/D43472

components/style/properties/gecko.mako.rs

@@ -345,10 +345,7 @@ def set_gecko_property(ffi_name, expr):
 </%def>
 
 <%def name="impl_keyword_clone(ident, gecko_ffi_name, keyword, cast_type='u8')">
-    // FIXME: We introduced non_upper_case_globals for -moz-appearance only
-    //        since the prefix of Gecko value starts with ThemeWidgetType_NS_THEME.
-    //        We should remove this after fix bug 1371809.
-    #[allow(non_snake_case, non_upper_case_globals)]
+    #[allow(non_snake_case)]
     pub fn clone_${ident}(&self) -> longhands::${ident}::computed_value::T {
         use crate::properties::longhands::${ident}::computed_value::T as Keyword;
         // FIXME(bholley): Align binary representations and ditch |match| for cast + static_asserts