Removes unwanted data migration (#280)

db/migrate/20170519091541_add_pic_to_inbox_migration.rb

@@ -1,24 +0,0 @@
-class AddPicToInboxMigration < ActiveRecord::Migration[5.0]
-  def change
-    FacebookPage.find_each do |inbox|
-      begin
-        url = 'http://graph.facebook.com/' << inbox.page_id << '/picture?type=large'
-        uri = URI.parse(url)
-        tries = 3
-        begin
-          response = uri.open(redirect: false)
-        rescue OpenURI::HTTPRedirect => e
-          uri = e.uri # assigned from the "Location" response header
-          retry if (tries -= 1) > 0
-          raise
-        end
-        pic_url = response.base_uri.to_s
-        puts pic_url.inspect
-      rescue StandardError => e
-        pic_url = nil
-      end
-      inbox.remote_avatar_url = pic_url
-      inbox.save!
-    end
-  end
-end