CurrentUser: remove #as method.

Replace with CurrentUser#scoped.

test/functional/moderator/dashboards_controller_test.rb

@@ -81,7 +81,7 @@ module Moderator
           setup do
             @users = (0..5).map {create(:user)}
 
-            CurrentUser.as(@users[0]) do
+            as(@users[0]) do
               @comment = create(:comment)
             end
 

test/test_helper.rb

@@ -60,7 +60,7 @@ class ActiveSupport::TestCase
   end
 
   def as(user, &block)
-    CurrentUser.as(user, &block)
+    CurrentUser.scoped(user, &block)
   end
 end
 

test/unit/danbooru_maintenance_test.rb

@@ -30,7 +30,7 @@ class DanbooruMaintenanceTest < ActiveSupport::TestCase
         banner = FactoryBot.create(:admin_user)
         user = FactoryBot.create(:user)
 
-        CurrentUser.as(banner) { FactoryBot.create(:ban, user: user, banner: banner, duration: 1) }
+        as(banner) { create(:ban, user: user, banner: banner, duration: 1) }
 
         assert_equal(true, user.reload.is_banned)
         travel_to(2.days.from_now) { DanbooruMaintenance.daily }