[clang-tools-extra] [clang-tidy] Adjust size-empty doc because C++11 size() is constant-time (PR #117629)

[Congcong Cai via cfe-commits]

HerrCai0907 wrote:

> In such case claim is still valid

I think we should remove the discussion about efficient in claim since it is misleading after C++11. For self-defined container, because implement of empty and size can be totally different, this claim is still misleading.


https://github.com/llvm/llvm-project/pull/117629