[Bug libstdc++/86013] std::vector::shrink_to_fit() could sometimes use realloc()

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86013

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
You're jumping through arcane hoops just to provide a property which is not
guaranteed by the function and was never intended to be supported. If you don't
want shrink_to_fit to reallocate then stop calling it.