[Clang] Fix status of P0960

P0960R3 and P1975R0 were marked not implemented because
of #61145,

This issue has been fixed and backported to LLVM 16,
the status page should reflect that.

Reviewed By: #clang-language-wg, ayzhao, erichkeane

Differential Revision: https://reviews.llvm.org/D150122