Delete enableFabricInLogBox flag

Summary:
This diff deletes the ReactFeatureFlag enableFabricInLogBox, from now on Logbox will be rendered in Fabric when Fabric is enabled

changelog: [internal] internal

Reviewed By: genkikondo

Differential Revision: D33781626

fbshipit-source-id: 3187a22fec80125afd27860995637564640dab8d

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java

@@ -336,7 +336,7 @@ public class ReactInstanceManager {
         Activity currentActivity = getCurrentActivity();
         if (currentActivity != null) {
           ReactRootView rootView = new ReactRootView(currentActivity);
-          rootView.setIsFabric(ReactFeatureFlags.enableFabricInLogBox);
+          rootView.setIsFabric(ReactFeatureFlags.enableFabricRenderer);
           rootView.startReactApplication(ReactInstanceManager.this, appKey, null);
           return rootView;
         }

ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java

@@ -99,9 +99,6 @@ public class ReactFeatureFlags {
     return useOverflowInset;
   }
 
-  /** Enables Fabric for LogBox */
-  public static boolean enableFabricInLogBox = false;
-
   public static boolean enableLockFreeEventDispatcher = false;
 
   public static boolean enableAggressiveEventEmitterCleanup = false;