[turbofan] Drop the obsolete TypeGuard operator.

src/compiler/effect-control-linearizer.cc

Index: src/compiler/effect-control-linearizer.cc
diff --git a/src/compiler/effect-control-linearizer.cc b/src/compiler/effect-control-linearizer.cc
index 5822d6e264bfe88c46f60a3b139ddc9d67568d86..ba381919298d1ccaa04366baac37e4714ac19058 100644
--- a/src/compiler/effect-control-linearizer.cc
+++ b/src/compiler/effect-control-linearizer.cc
@@ -395,9 +395,6 @@ bool EffectControlLinearizer::TryWireInStateEffect(Node* node,
                                                    Node** control) {
   ValueEffectControl state(nullptr, nullptr, nullptr);
   switch (node->opcode()) {
-    case IrOpcode::kTypeGuard:
-      state = LowerTypeGuard(node, *effect, *control);
-      break;
     case IrOpcode::kChangeBitToTagged:
       state = LowerChangeBitToTagged(node, *effect, *control);
       break;
@@ -510,13 +507,6 @@ bool EffectControlLinearizer::TryWireInStateEffect(Node* node,
 }
 
 EffectControlLinearizer::ValueEffectControl
-EffectControlLinearizer::LowerTypeGuard(Node* node, Node* effect,
-                                        Node* control) {
-  Node* value = node->InputAt(0);
-  return ValueEffectControl(value, effect, control);
-}
-
-EffectControlLinearizer::ValueEffectControl
 EffectControlLinearizer::LowerChangeFloat64ToTagged(Node* node, Node* effect,
                                                     Node* control) {
   Node* value = node->InputAt(0);