fix(types): support typing if storage= is not passed (#604)

Author: henryiii

src/boost_histogram/_internal/hist.py

@@ -150,8 +150,8 @@ def __init__(self, *args: CppHistogram, metadata: Any = ...) -> None:
     def __init__(
         self,
         *axes: Union[Axis, CppAxis],
-        storage: Storage,
-        metadata: Any = None,
+        storage: Storage = ...,
+        metadata: Any = ...,
     ) -> None:
         ...