were only useful before C++14.

Callers should use `std::exchange`, `std::forward` and `std::move`
instead.

One thing to note is that some compilers issue warnings about pessimizing
and redundant moves. Some compilers were able to apply this analysis to
std::move but not absl::move. If you get a warning about one of these issues
now that absl::move is an alias for std::move, you should remove this use of
move.
See https://developers.redhat.com/blog/2019/04/12/understanding-when-not-to-stdmove-in-c
PiperOrigin-RevId: 621861324
Change-Id: I60f98b59be5ff425bd17fbce43d9218c361720c2