[Turbofan] Fixed a reducer returning Changed() instead of NoChange()

The JSTypedLowering reducer was returning Changed(node) when it
did not change the node, in case the node was a speculative number
comparison node.

Bug: 
Change-Id: I2082e4c2e45078b343e427f54d61d4e0a323a64f
Reviewed-on: https://chromium-review.googlesource.com/568036Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Alexandre Talon <alexandret@google.com>
Cr-Commit-Position: refs/heads/master@{#46600}

src/compiler/js-typed-lowering.cc

@@ -915,7 +915,7 @@ Reduction JSTypedLowering::ReduceSpeculativeNumberComparison(Node* node) {
       r.BothInputsAre(Type::Unsigned32())) {
     return r.ChangeToPureOperator(r.NumberOpFromSpeculativeNumberOp());
   }
-  return Changed(node);
+  return NoChange();
 }
 
 Reduction JSTypedLowering::ReduceJSComparison(Node* node) {