[turbofan] Drop the obsolete TypeGuard operator.

src/compiler/simplified-operator-reducer.cc

Index: src/compiler/simplified-operator-reducer.cc
diff --git a/src/compiler/simplified-operator-reducer.cc b/src/compiler/simplified-operator-reducer.cc
index 5db9dfbf5660db5a9be31f146bb1d4965eaf0619..b9d5c268d180735d779af8e7141e466bb8a107ce 100644
--- a/src/compiler/simplified-operator-reducer.cc
+++ b/src/compiler/simplified-operator-reducer.cc
@@ -175,8 +175,6 @@ Reduction SimplifiedOperatorReducer::Reduce(Node* node) {
     }
     case IrOpcode::kReferenceEqual:
       return ReduceReferenceEqual(node);
-    case IrOpcode::kTypeGuard:
-      return ReduceTypeGuard(node);
     default:
       break;
   }
@@ -199,15 +197,6 @@ Reduction SimplifiedOperatorReducer::ReduceReferenceEqual(Node* node) {
   return NoChange();
 }
 
-Reduction SimplifiedOperatorReducer::ReduceTypeGuard(Node* node) {
-  DCHECK_EQ(IrOpcode::kTypeGuard, node->opcode());
-  Node* const input = NodeProperties::GetValueInput(node, 0);
-  Type* const input_type = NodeProperties::GetTypeOrAny(input);
-  Type* const guard_type = TypeOf(node->op());
-  if (input_type->Is(guard_type)) return Replace(input);
-  return NoChange();
-}
-
 Reduction SimplifiedOperatorReducer::Change(Node* node, const Operator* op,
                                             Node* a) {
   DCHECK_EQ(node->InputCount(), OperatorProperties::GetTotalInputCount(op));