removes controller spec deprecation warnings

spec/controllers/users/registrations_controller_spec.rb

@@ -10,7 +10,7 @@ describe Users::RegistrationsController do
 
     context "when username is available" do
       it "returns true with no error message" do
-        get :check_username, username: "available username"
+        get :check_username, params: { username: "available username" }
 
         data = JSON.parse response.body, symbolize_names: true
         expect(data[:available]).to be true
@@ -21,7 +21,7 @@ describe Users::RegistrationsController do
     context "when username is not available" do
       it "returns false with an error message" do
         user = create(:user)
-        get :check_username, username: user.username
+        get :check_username, params: { username: user.username }
 
         data = JSON.parse response.body, symbolize_names: true
         expect(data[:available]).to be false