tests: fix post expungement test.

Delay jobs so the uploaded file isn't deleted immediately (see f6c928e660).

test/unit/post_test.rb

@@ -27,11 +27,16 @@ class PostTest < ActiveSupport::TestCase
   context "Deletion:" do
     context "Expunging a post" do
       setup do
+        Delayed::Worker.delay_jobs = true
         @upload = UploadService.new(FactoryBot.attributes_for(:jpg_upload)).start!
         @post = @upload.post
         Favorite.add(post: @post, user: @user)
       end
 
+      teardown do
+        Delayed::Worker.delay_jobs = false
+      end
+
       should "delete the files" do
         assert_nothing_raised { @post.file(:preview) }
         assert_nothing_raised { @post.file(:original) }