[ValueTracking][NFC] Drop outdated TODO in canCreateUndefOrPoison (#139915)

The inrange constexpr GEP case is handled since 425cbbc.

Author: c-rhodes

llvm/lib/Analysis/ValueTracking.cpp

@@ -7786,10 +7786,7 @@ static bool canCreateUndefOrPoison(const Operator *Op, UndefPoisonKind Kind,
   case Instruction::FMul:
   case Instruction::FDiv:
   case Instruction::FRem:
-    return false;
   case Instruction::GetElementPtr:
-    // inbounds is handled above
-    // TODO: what about inrange on constexpr?
     return false;
   default: {
     const auto *CE = dyn_cast<ConstantExpr>(Op);