[pywin32] Update LookupAccountSid to accept None for systemName (#14484)

Author: brianschubert

stubs/pywin32/win32/win32security.pyi

@@ -41,7 +41,7 @@ def LogonUserEx(
     Username: str, Domain: str, Password: str, LogonType, LogonProvider
 ) -> tuple[int, _win32typing.PySID, Incomplete, Incomplete]: ...
 def LookupAccountName(systemName: str | None, accountName: str, /) -> tuple[_win32typing.PySID, str, int]: ...
-def LookupAccountSid(systemName: str, sid: _win32typing.PySID, /) -> tuple[str, str, Incomplete]: ...
+def LookupAccountSid(systemName: str | None, sid: _win32typing.PySID, /) -> tuple[str, str, Incomplete]: ...
 def GetBinarySid(SID: str, /) -> _win32typing.PySID: ...
 def SetSecurityInfo(
     handle: int,