FIX: Stop updating bookmarked column from TopicUser.update_post_action_cache (#10188)

* This is causing issues where sometimes bookmarked is out of sync with what is in the Bookmark table. The BookmarkManager handles updating this column now.
* Add migration to fix bookmarked column that is incorrectly marked false when a Bookmark record exists.

db/migrate/20200708035330_fix_topic_user_bookmarked_sync_issues.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class FixTopicUserBookmarkedSyncIssues < ActiveRecord::Migration[6.0]
+  def up
+    sql = <<~SQL
+      UPDATE topic_users SET bookmarked = true WHERE id IN (
+        SELECT topic_users.id
+        FROM topic_users
+        INNER JOIN bookmarks ON bookmarks.user_id = topic_users.user_id AND
+          bookmarks.topic_id = topic_users.topic_id
+        WHERE NOT topic_users.bookmarked
+      ) AND NOT bookmarked
+    SQL
+    DB.exec(sql)
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end