Remove redundant breaking change notice for Map<Object?, Object?> change

The analyzer accepts `Map` and `Map<Object?, Object?>` without restrictions. Thus this is actually not a breaking change.

 ## NEXT
-Breaking changes:
-* The internal `fromNative()` methods now accept a `Map<Object?, Object?>` instead of `Map<dynamic, dynamic>`.
-
 Improvements:
 * The `type` of an `Address` is now non-null.
 * The `type` of an `Email` is now non-null.