DEV: Fix sidekiq requires in test env

When in test env, we can get errors because the "sidekiq/api" file isn’t
properly loaded.

app/jobs/base.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "sidekiq/api"
+
 module Jobs
   def self.queued
     Sidekiq::Stats.new.enqueued

lib/backup_restore/system_interface.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "sidekiq/api"
+
 module BackupRestore
   class RunningSidekiqJobsError < RuntimeError
     def initialize

lib/discourse_dev/topic.rb

@@ -2,6 +2,7 @@
 
 require "discourse_dev/record"
 require "faker"
+require "sidekiq/api"
 
 module DiscourseDev
   class Topic < Record