[turbofan] Drop the obsolete TypeGuard operator.

src/compiler/verifier.cc

Index: src/compiler/verifier.cc
diff --git a/src/compiler/verifier.cc b/src/compiler/verifier.cc
index ed32b4fb603b93a5907bdafca226d0117f6043b4..48f947d62ef2daf98dfe0e0a982787ed6ea9b96e 100644
--- a/src/compiler/verifier.cc
+++ b/src/compiler/verifier.cc
@@ -417,9 +417,6 @@ void Verifier::Visitor::Check(Node* node) {
       CHECK_EQ(input_count, 1 + effect_count);
       break;
     }
-    case IrOpcode::kTypeGuard:
-      // TODO(bmeurer): what are the constraints on these?
-      break;
     case IrOpcode::kCheckpoint:
       // Type is empty.
       CheckNotTyped(node);