US 173-283 29.10.3 [simd.syn] Fix declaration of `compress`

[wg21bot]

Last overload of compress in the synopsis should say M::value_type and not V.

Proposed change:

Modify accordingly.

[timsong-cpp]

This is editorial and already fixed by cplusplus/draft@9db1d3b

[jensmaurer]

Accepted.