[span.syn] `remove_cv_ref_t` in concept `integral-constant-like` should be `remove_cvref_t`

https://eel.is/c++draft/span.syn#concept:integral-constant-like

> ```cpp
>      is_integral_v<remove_cv_ref_t<decltype(T::value)>> &&
> ```

Though concept `integral-constant-like` says to be "exposition only", definition inside should not be misspelled (`remove_cv_ref_t` => `remove_cvref_t`).