Merge branch '63710-fix-redis-namespace-warning' into 'master'

Trigger flushdb in a way that redis-namespace is happy with

Closes #63710

See merge request gitlab-org/gitlab-ce!30039

spec/support/sidekiq.rb

@@ -30,6 +30,8 @@ RSpec.configure do |config|
   end
 
   config.after(:each, :sidekiq, :redis) do
-    Sidekiq.redis { |redis| redis.flushdb }
+    Sidekiq.redis do |connection|
+      connection.redis.flushdb
+    end
   end
 end