[clang] Bugfix for chosing the correct deduction guide (PR #66487)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

This seems right to me, however we need to do 2 things:

1- This needs a release note.

2- We need to track down when this changed in the standard, and why.  If it was a DR, we need to do make sure we update that we've implemented that DR.  If it was a normal paper, we need to figure out which versions of the standard it applies to and do THAT correctly.  Either way, we'd have to update the paper tracking doc.

https://github.com/llvm/llvm-project/pull/66487