[libcxx-commits] [libcxx] [libc++][string] Fixes shrink_to_fit. (PR #97961)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

LGTM. Changes of this nature to `std::string` are always really tricky. Let's keep an eye out for unintended fallout, and if anything happens, we should likely revert and try landing this into LLVM 20 instead, even though it means that `vector` and `string` will behave differently w.r.t. `shrink_to_fit`.

https://github.com/llvm/llvm-project/pull/97961