Fix return type of Distribution.origin property (#14648)

Author: Viicos

stdlib/importlib/metadata/__init__.pyi

@@ -257,7 +257,7 @@ class Distribution(_distribution_parent):
         def name(self) -> str: ...
     if sys.version_info >= (3, 13):
         @property
-        def origin(self) -> types.SimpleNamespace: ...
+        def origin(self) -> types.SimpleNamespace | None: ...
 
 class DistributionFinder(MetaPathFinder):
     class Context: