Revert "Use `add_directory_column` API to add solutions count to user directory (#137)" (#139)

This reverts commit 58c594fdda.

config/locales/client.en.yml

@@ -4,7 +4,6 @@ en:
       alt:
         solved:
           accepted_notification: "accepted"
-    solutions: "Solutions"
 
     solved:
       title: "Solved"

db/migrate/20210609171830_add_solutions_to_directory_items.rb

@@ -1,7 +0,0 @@
-# frozen_string_literal: true
-
-class AddSolutionsToDirectoryItems < ActiveRecord::Migration[6.1]
-  def change
-    add_column :directory_items, :solutions, :integer, default: 0
-  end
-end

plugin.rb

@@ -613,26 +613,6 @@ SQL
     options[:refresh_stream] = true if old_category_allows != new_category_allows
   end
 
-  query = "
-    WITH x AS (SELECT
-      u.id user_id,
-      COUNT(DISTINCT ua.id) AS solutions
-      FROM users AS u
-      INNER JOIN user_actions AS ua ON ua.user_id = u.id AND ua.action_type = #{UserAction::SOLVED} AND COALESCE(ua.created_at, :since) > :since
-      WHERE u.active
-        AND u.silenced_till IS NULL
-        AND u.id > 0
-      GROUP BY u.id
-    )
-    UPDATE directory_items di SET
-      solutions = x.solutions
-    FROM x
-    WHERE x.user_id = di.user_id
-    AND di.period_type = :period_type
-    AND di.solutions <> x.solutions
-  "
-  add_directory_column("solutions", query: query)
-
   add_to_class(:composer_messages_finder, :check_topic_is_solved) do
     return if !SiteSetting.solved_enabled || SiteSetting.disable_solved_education_message
     return if !replying? || @topic.blank? || @topic.private_message?