Also remove some bogus `std::forward`s. My impression is that these
forwards were actually harmless, because `ranges::begin(FWD(t))` is
always identical to `ranges::begin(t)` (except when it's ill-formed,
and that can't happen in this case). However, they're also superfluous
and don't reflect the wording in the standard, so let's eliminate them.
Differential Revision: https://reviews.llvm.org/D117043
For example, `std::ranges::range<Holder<Incomplete>*>` should be
well-formed false, not a hard error at compile time.
Differential Revision: https://reviews.llvm.org/D116239