Fix instance comparison in AbsMax and AbsMin classes

- Changed identity comparison (is not) to instance checking (isinstance)
  - Fixes incorrect behavior when comparing instances of same class

Author: Sunny Nguyen

src/validators/_extremes.py

@@ -23,7 +23,7 @@ class AbsMax:
 
     def __ge__(self, other: Any):
         """GreaterThanOrEqual."""
-        return other is not AbsMax
+        return not isinstance(other, AbsMax)
 
 
 @total_ordering
@@ -44,4 +44,4 @@ class AbsMin:
 
     def __le__(self, other: Any):
         """LessThanOrEqual."""
-        return other is not AbsMin
+        return not isinstance(other, AbsMin)