Recommend Never for return types as well

[srittau]

Per discussion in python/cpython#132941

[ngnpope]

This change updated this section, but there are other places that should probably also be reworded:

https://typing.python.org/en/latest/spec/special-types.html#never has the following:

The Never type is equivalent to NoReturn, which is discussed above. The NoReturn type is conventionally used in return annotations of functions, and Never is typically used in other locations, but the two types are completely interchangeable.

https://typing.python.org/en/latest/spec/special-types.html#noreturn should probably also say that Never is preferred.

https://typing.python.org/en/latest/spec/constructors.html has some references to NoReturn that could be changed to Never?

On the https://typing.python.org/en/latest/spec/special-types.html page, perhaps Never should come above NoReturn and the examples for NoReturn should be moved to Never, with NoReturn being a simple statement saying that Never is preferred?