[llvm] Revert "[STLExtras] Remove incorrect hack to make indexed_accessor_range operator== compatible with C++20" (PR #72265)

[Utkarsh Saxena via llvm-commits]

usx95 wrote:

Thanks for the clarification. I was not aware of that practice.
FWIW, Github offers to revert a PR with 2-clicks which is extremely convenient (1. create revert PR, 2. merge). If we are not to follow this for LLVM (because PR implies a code review), we should mention not to use this method in the [docs] (https://llvm.org/docs/GitHub.html)

https://github.com/llvm/llvm-project/pull/72265