Fix comment in FrameLoaderStateMachine

FirstLayoutDone state was removed long time ago in
https://chromiumcodereview.appspot.com/14787005, change the comment to
reflect the current states.

Bug: None
Change-Id: Idac41a01e3f85d8187eae8c8ea89ba1a576f3096
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1802522
Commit-Queue: Shimi Zhang <ctzsm@chromium.org>
Reviewed-by: Nate Chapin <japhet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697024}

third_party/blink/renderer/core/loader/frame_loader_state_machine.h

@@ -46,9 +46,7 @@ class CORE_EXPORT FrameLoaderStateMachine {
  public:
   FrameLoaderStateMachine();
 
-  // Once a load has been committed, the state may alternate between
-  // CommittedFirstRealLoad and FirstLayoutDone. Otherwise, the states only go
-  // down the list.
+  // The states only go down the list.
   enum State {
     kCreatingInitialEmptyDocument,
     kDisplayingInitialEmptyDocument,