[NFC] Remove outdated TODO for `Type::getPointerTo`

[JOE1994]

Summary

D104718 (commit 7bb7fa12e73b) introduced the TODO comment, along with
code for opaque pointer handling in Type::getPointerTo.

Later, D104902 (commit 1e6303e60ca5) removed the separate opaque pointer
handling code in Type::getPointerTo. Thus, getting rid of
Type::getPointerTo seems no longer unnecessary.

[JOE1994]

Minor fix to commit message.

[nikic]

The TODO is still relevant. This method will be removed when migration finishes, as it is no longer needed.

[JOE1994]

The TODO is still relevant.

Since the function getPointerTo was added back in 2015 (commit 84a138a351d665332477e807b4292c1b1f7dd523),
I assumed that the sole motivation for removing getPointerTo is because of the extra code block for handling opaque pointers.

If the plan is to eventually get rid of getPointerTo, so I'll close this revision.

llvm/include/llvm/IR/Type.h

 //===- llvm/Type.h - Classes for handling data types ------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
public:
   static PointerType *getInt16PtrTy(LLVMContext &C, unsigned AS = 0);
   static PointerType *getInt32PtrTy(LLVMContext &C, unsigned AS = 0);
   static PointerType *getInt64PtrTy(LLVMContext &C, unsigned AS = 0);
   static Type *getWasm_ExternrefTy(LLVMContext &C);
   static Type *getWasm_FuncrefTy(LLVMContext &C);
 
   /// Return a pointer to the current type. This is equivalent to
   /// PointerType::get(Foo, AddrSpace).
-  /// TODO: Remove this after opaque pointer transition is complete.
   PointerType *getPointerTo(unsigned AddrSpace = 0) const;
 
 private:
   /// Derived types like structures and arrays are sized iff all of the members
   /// of the type are sized as well. Since asking for their size is relatively
   /// uncommon, move this operation out-of-line.
   bool isSizedDerivedType(SmallPtrSetImpl<Type*> *Visited = nullptr) const;
 };