Remove legacy layout diffing

Summary:
This removes some unused flags which will cause Yoga to layout every tree twice, then diffing the tree, reporting whether the whole tree is different. This is too expensive to run outside of local experimentation, but we have more nuanced ways to implement the `YGNodeLayoutAffectedByQuirk` I am wanting to add.

Changelog: [Internal]

Reviewed By: lunaleaps

Differential Revision: D42406917

fbshipit-source-id: b415ed02768f6b59de3a6fa90c60c750d56fd4b0

yoga/YGNode.h

@@ -327,8 +327,6 @@ public:
       const float mainSize,
       const float crossSize,
       const float ownerWidth);
-  void setLayoutDoesLegacyFlagAffectsLayout(bool doesLegacyFlagAffectsLayout);
-  void setLayoutDidUseLegacyFlag(bool didUseLegacyFlag);
   void markDirtyAndPropogateDownwards();
 
   // Other methods
@@ -351,8 +349,6 @@ public:
   float resolveFlexGrow() const;
   float resolveFlexShrink() const;
   bool isNodeFlexible();
-  bool didUseLegacyFlag();
-  bool isLayoutTreeEqualToNode(const YGNode& node) const;
   void reset();
 };