Make operator == parameter non-nullable (flutter#38663)

Author: srawlins

lib/web_ui/lib/src/engine/canvaskit/noto_font.dart

@@ -65,7 +65,7 @@ class CodeunitRange {
   }
 
   @override
-  bool operator ==(dynamic other) {
+  bool operator ==(Object other) {
     if (other is! CodeunitRange) {
       return false;
     }