Use TypeAlias where possible for type aliases (#7630)

stdlib/fractions.pyi

@@ -3,9 +3,9 @@ from _typeshed import Self
 from decimal import Decimal
 from numbers import Integral, Rational, Real
 from typing import Any, overload
-from typing_extensions import Literal
+from typing_extensions import Literal, TypeAlias
 
-_ComparableNum = int | float | Decimal | Real
+_ComparableNum: TypeAlias = int | float | Decimal | Real
 
 if sys.version_info >= (3, 9):
     __all__ = ["Fraction"]