[range.reverse.overview] Improve wording

views::reverse is specialized for reverse_view and subrange. However, we check with:

Given a subexpression E, the expression views​::​reverse(E) is expression-equivalent to:
(2.1) If the type of E is a (possibly cv-qualified) specialization of reverse_view, ...
(2.2) Otherwise, if the type of E is cv subrange<reverse_iterator<I>, reverse_iterator<I>, K> for some iterator type I and value K of type subrange_kind, ...

This is not the wording commonly used in <ranges> to determine specialization; we usually introduce a new type T and use something like this:

Given a subexpression E, let T be remove_cvref_t<decltype((E))>. views​::​reverse(E) is expression-equivalent to:
(2.1) If T denotes reverse_view, ...
(2.2) Otherwise, if T denotes subrange<reverse_iterator<I>, reverse_iterator<I>, K> for some iterator type I and value K of type subrange_kind, ...

See [range.take.overview], [range.drop.overview], [range.as.const.overview].

Start at [range.reverse.overview] and compare its specialization wording with [range.take.overview], [range.drop.overview], and [range.as.const.overview]. Done means the reverse wording consistently introduces T as remove_cvref_t<decltype((E))> and uses T to describe the reverse_view and subrange cases.