C++ style enums 15/N: Display (#1397)

Summary:
X-link: https://github.com/facebook/react-native/pull/39541

Pull Request resolved: https://github.com/facebook/yoga/pull/1397

Moves internal usages of YGDisplay to Display

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Changelog: [Internal]

Reviewed By: sammy-SC

Differential Revision: D49361952

fbshipit-source-id: a961efaa35a3fed01659d23783bf90e0b47656f0

yoga/debug/NodeToString.cpp

@@ -174,8 +174,7 @@ void nodeToString(
     }
 
     if (style.display() != yoga::Node{}.getStyle().display()) {
-      appendFormattedString(
-          str, "display: %s; ", YGDisplayToString(style.display()));
+      appendFormattedString(str, "display: %s; ", toString(style.display()));
     }
     appendEdges(str, "margin", style.margin());
     appendEdges(str, "padding", style.padding());