Downgrade to Redis 3.2.2 due to massive memory leak with Sidekiq

See:

https://github.com/mperham/sidekiq/blob/master/Changes.md#413
https://gitlab.com/gitlab-org/gitlab-ce/issues/19441

CHANGELOG

@@ -36,6 +36,7 @@ v 8.9.5 (unreleased)
   - Improve the request / withdraw access button. !4860
   - Fix assigning shared runners as admins. !4961
   - Show "locked" label for locked runners on runners admin. !4961
+  - Downgrade to Redis 3.2.2 due to massive memory leak with Sidekiq
   - Fixes issues importing events in Import/Export. Import/Export version bumped to 0.1.1
   - Fix import button disabled when import process fail due to the namespace already been taken.
 

Gemfile.lock

@@ -554,7 +554,7 @@ GEM
     recaptcha (3.0.0)
       json
     redcarpet (3.3.3)
-    redis (3.3.0)
+    redis (3.2.2)
     redis-actionpack (4.0.1)
       actionpack (~> 4)
       redis-rack (~> 1.5.0)