[clang] Revert [clang] Handle templated operators with reversed arguments and [STLExtras] Undo C++20 hack (PR #69937)

[Nico Weber via cfe-commits]

nico wrote:

Looks like the revert broke tests: http://45.33.8.238/linux/121332/step_7.txt

Please take a look.

https://github.com/llvm/llvm-project/pull/69937