Fix RuboCop offense Rails/WhereMissing (#37248).

git-svn-id: https://svn.redmine.org/redmine/trunk@21927 e93f8b46-1217-0410-a6f0-8f06a7374b81

db/migrate/20220224194639_delete_orphaned_time_entry_activities.rb

@@ -1,6 +1,6 @@
 class DeleteOrphanedTimeEntryActivities < ActiveRecord::Migration[6.1]
   def self.up
-    TimeEntryActivity.left_outer_joins(:project).where(projects: {id: nil}).where.not(project_id: nil).delete_all
+    TimeEntryActivity.where.missing(:project).where.not(project_id: nil).delete_all
   end
 
   def self.down