Fix Active Job Sidekiq integration tests

The `Sidekiq::Logging` module was removed in Sidekiq 6.0 in favour of
`Sidekiq.logger=`.

https://github.com/mperham/sidekiq/wiki/Logging#api-changes

> The old Sidekiq::Logging class was removed in Sidekiq 6.0. You should
> not be accessing any Sidekiq internal classes to use the logger. Use
> `logger` directly in your Worker or use `Sidekiq.logger` elsewhere.

Gemfile.lock

@@ -389,7 +389,7 @@ GEM
       ffi (~> 1.0)
     rdoc (6.0.4)
     redcarpet (3.2.3)
-    redis (4.1.1)
+    redis (4.1.2)
     redis-namespace (1.6.0)
       redis (>= 3.0.4)
     regexp_parser (1.6.0)
@@ -448,10 +448,11 @@ GEM
     sequel (5.14.0)
     serverengine (2.0.7)
       sigdump (~> 0.2.2)
-    sidekiq (5.2.3)
-      connection_pool (~> 2.2, >= 2.2.2)
-      rack-protection (>= 1.5.0)
-      redis (>= 3.3.5, < 5)
+    sidekiq (6.0.0)
+      connection_pool (>= 2.2.2)
+      rack (>= 2.0.0)
+      rack-protection (>= 2.0.0)
+      redis (>= 4.1.0)
     sigdump (0.2.4)
     signet (0.11.0)
       addressable (~> 2.3)

activejob/test/support/integration/adapters/sidekiq.rb

@@ -36,7 +36,7 @@ module SidekiqJobsManager
       $stderr.sync = true
 
       logfile = Rails.root.join("log/sidekiq.log").to_s
-      Sidekiq::Logging.initialize_logger(logfile)
+      Sidekiq.logger = Sidekiq::Logger.new(logfile)
 
       self_read, self_write = IO.pipe
       trap "TERM" do