[clang] [llvm] [NFC] Remove Type::getInt8PtrTy (PR #71029)

[Paulo Matos via cfe-commits]

pmatos wrote:

> I still think all the defaulted address space parameters should be purged and it only invites bugs. It's a regression to introduce a new defaulted argument.

Understandable, although always writing `PointerType::get(Ctx, 0);` really looks weird given most of the time the second parameter is 0. So it just feels like it's a special constant that will suddenly be sprinkled all over the code.

https://github.com/llvm/llvm-project/pull/71029