[clang] [Clang][Sema] Reject template arguments not equivalent to their copies (part of P2308R1) (PR #193754)

[Shafik Yaghmour via cfe-commits]

================
@@ -49,6 +49,8 @@ C++ Specific Potentially Breaking Changes
 - Clang now correctly rejects ``export`` declarations in module implementation
   partitions. (#GH107602)
 
+- Template arguments which aren't equivalent to their copies are correctly rejected.
----------------
shafik wrote:

```suggestion
- Template arguments which aren't template-argument-equivalent to their copies are correctly rejected.
```

https://github.com/llvm/llvm-project/pull/193754