Add default values for third-party stubs beginning with 'P' (#9957)

stubs/pywin32/isapi/__init__.pyi

@@ -4,7 +4,7 @@ class ISAPIError(Exception):
     errno: Incomplete
     strerror: Incomplete
     funcname: Incomplete
-    def __init__(self, errno, strerror: Incomplete | None = ..., funcname: Incomplete | None = ...) -> None: ...
+    def __init__(self, errno, strerror: Incomplete | None = None, funcname: Incomplete | None = None) -> None: ...
 
 class FilterError(ISAPIError): ...
 class ExtensionError(ISAPIError): ...