Replace non-ellipsis default arguments (#2550)

stdlib/2and3/fractions.pyi

@@ -4,7 +4,7 @@
 # Note: these stubs are incomplete. The more complex type
 # signatures are currently omitted. Also see numbers.pyi.
 
-from typing import Optional, TypeVar, Union, overload
+from typing import Optional, TypeVar, Union, overload, Any
 from numbers import Real, Integral, Rational
 from decimal import Decimal
 import sys
@@ -74,7 +74,7 @@ class Fraction(Rational):
     if sys.version_info >= (3, 0):
         def __floor__(self) -> int: ...
         def __ceil__(self) -> int: ...
-        def __round__(self, ndigits=None): ...
+        def __round__(self, ndigits: Optional[Any] = ...): ...
 
     def __hash__(self) -> int: ...
     def __eq__(self, other: object) -> bool: ...

stdlib/2and3/numbers.pyi

@@ -5,7 +5,7 @@
 # Note: these stubs are incomplete. The more complex type
 # signatures are currently omitted.
 
-from typing import Optional, SupportsFloat
+from typing import Any, Optional, SupportsFloat
 from abc import ABCMeta, abstractmethod
 import sys
 
@@ -110,7 +110,7 @@ class Integral(Rational):
         def __long__(self) -> long: ...
     def __index__(self) -> int: ...
     @abstractmethod
-    def __pow__(self, exponent, modulus=None): ...
+    def __pow__(self, exponent, modulus: Optional[Any] = ...): ...
     @abstractmethod
     def __lshift__(self, other): ...
     @abstractmethod