Remove unused columns from tweets (#7128)

Co-authored-by: Ben Halpern <bendhalpern@gmail.com>

app/models/tweet.rb

@@ -1,7 +1,4 @@
 class Tweet < ApplicationRecord
-  self.ignored_columns = %w[
-    primary_external_url
-  ]
   mount_uploader :profile_image, ProfileImageUploader
 
   belongs_to :user, optional: true

db/migrate/20200407090218_remove_unused_columns_from_tweets.rb

@@ -0,0 +1,7 @@
+class RemoveUnusedColumnsFromTweets < ActiveRecord::Migration[5.2]
+  def change
+    safety_assured do
+      remove_column :tweets, :primary_external_url, :string
+    end
+  end
+end

db/schema.rb

@@ -1040,7 +1040,6 @@ ActiveRecord::Schema.define(version: 2020_04_07_091449) do
     t.datetime "last_fetched_at"
     t.text "media_serialized", default: "--- []\n"
     t.string "mentioned_usernames_serialized", default: "--- []\n"
-    t.string "primary_external_url"
     t.string "profile_image"
     t.string "quoted_tweet_id_code"
     t.integer "retweet_count"