Emit assignment-from-no-return instead of assignment-from-none for implicitly returning stdlib calls

[jacobtylerwalls]

"Assignment from no return" is essentially the same as "assignment from none". I don't see the point of maintaining a distinction.

Besides suggesting that there is a distinction, we might also cause confusion with typing.NoReturn which signifies not an implicit return but always raising.

Suggest that in 3.0 we start always emitting assignment-from-none and mark assignment-from-no-return as a historical name.

[jacobtylerwalls]

Discussed here: we won't merge the two checks, since storing a None from a function with explicit returns might be informative.

In that case, we need to emit the correct message (assignment-from-no-return) for stdlib calls like dict.update() and list.sort() -- see #8809 and #5738.