[llvm] [TargetLowering] remove unused virtual from ComputeConstraintToUse (PR #67171)

[Nick Desaulniers via llvm-commits]

nickdesaulniers wrote:

IIUC, looks like I need to fix the cmake rules for `llvm-extract` as well.
```
8367/9684] Linking CXX executable bin\llvm-extract.exe
--
  | FAILED: bin/llvm-extract.exe
```

https://github.com/llvm/llvm-project/pull/67171