MAINT: add newaxis to __all__ in numpy.array_api

Follows up on a post-merge comment in gh-25146.

[skip ci]

Original NumPy Commit: 066b901b76b89a529a09588c129d79c832bffc6a

Author: rgommers

array_api_strict/__init__.py

@@ -127,7 +127,7 @@
 
 from ._constants import e, inf, nan, pi, newaxis
 
-__all__ += ["e", "inf", "nan", "pi"]
+__all__ += ["e", "inf", "nan", "pi", "newaxis"]
 
 from ._creation_functions import (
     asarray,