Remove interface

Author: mrwillis21

encoders/firebase-encoders-json/src/json/java/com/google/firebase/encoders/json/JsonValueObjectEncoderContext.java

@@ -31,11 +31,6 @@
 
 final class JsonValueObjectEncoderContext implements ObjectEncoderContext, ValueEncoderContext {
 
-  private interface AddMethod {
-    JsonValueObjectEncoderContext invoke(@NonNull String name, @Nullable Object o)
-        throws IOException, EncodingException;
-  }
-
   private JsonValueObjectEncoderContext childContext = null;
   private boolean active = true;
   private final JsonWriter jsonWriter;