[llvm] [IR] Remove deprecated PointerType methods that always return true (PR #74521)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

so the commit message can contain migration instructions (yes the migration instructions are also on the declarations but this makes it just a bit easier for people who just want to look at the commit message)

https://github.com/llvm/llvm-project/pull/74521