Use `LLVMDisposeTargetMachine` After bumping the minimum LLVM version to 20 (rust-lang/rust#145071), we no longer need to run any custom code when disposing of a TargetMachine, so we can just use the upstream LLVM-C function.
Use `LLVMDisposeTargetMachine` After bumping the minimum LLVM version to 20 (rust-lang/rust#145071), we no longer need to run any custom code when disposing of a TargetMachine, so we can just use the upstream LLVM-C function.