Fix #5104 - GET /api/v1/apps/verify_credentials to confirm app works (#5112)

app/controllers/api/v1/apps_controller.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 class Api::V1::AppsController < Api::BaseController
-  respond_to :json
-
   def create
     @app = Doorkeeper::Application.create!(application_options)
     render json: @app, serializer: REST::ApplicationSerializer