[clang] Fix false positive of [[clang::require_explicit_initialization]] on copy/move constructors (PR #126553)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> Oh - @AaronBallman would you mind tagging this for the release so we can cherry pick?

Sure!

https://github.com/llvm/llvm-project/pull/126553