Remove useVanillaJNI flag and usage of fbjni in yoga build

Summary:
## Changelog:

[General] [Yoga] - Use vanilla jni instead of fbjni for all the jni communication

Reviewed By: astreet

Differential Revision: D17808005

fbshipit-source-id: 5e9a1ed73978f519c71c248774a28e5a294e7c7f

ReactAndroid/src/main/java/com/facebook/yoga/YogaNodeFactory.java

@@ -12,10 +12,6 @@ public abstract class YogaNodeFactory {
     return new YogaNodeJNIFinalizer();
   }
 
-  public static YogaNode create(boolean useVanillaJNI) {
-    return new YogaNodeJNIFinalizer(useVanillaJNI);
-  }
-
   public static YogaNode create(YogaConfig config) {
     return new YogaNodeJNIFinalizer(config);
   }