[clang] [clang] fix broken canonicalization of DeducedTemplateSpecializationType (PR #95202)

[Haojian Wu via cfe-commits]

https://github.com/hokein commented:

good catch, the fix looks good to me overall, I will leave the final stamp to @ChuanqiXu9.

(I agree that it would be nice to have a regression test if it is not too hard to reduce from libcxx)

https://github.com/llvm/llvm-project/pull/95202