[clang] Rename [[clang::requires_explicit_initialization]] to [[clang::require_explicit_initialization]] (PR #122947)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

I'll land the changes once pre-commit CI comes back green (I expect it will; I didn't spot any places that were missed)

https://github.com/llvm/llvm-project/pull/122947