Sidekiq::MemoryKiller: Add missing space in log message

The sidekiq memory killer prints warnings like

gitlab-sidekiq[8245]: 2017-09-27T11:31:43.192Z 8245 TID-ov9l6b4e0 WARN:
this thread will shut down PID 8245 - Worker ProjectWebHookWorker -
JID-dd3b1c23a653deec5e575ab4in 900 seconds

There is a space missing between the JID and 'in'.

changelogs/unreleased/14553-missing-space-in-log-msg.yml

+---
+title: "Add missing space in Sidekiq memory killer log message"
+merge_request: 14553
+author: Benjamin Drung
+type: fixed

lib/gitlab/sidekiq_middleware/memory_killer.rb

@@ -25,7 +25,7 @@ module Gitlab
 
           Sidekiq.logger.warn "current RSS #{current_rss} exceeds maximum RSS "\
             "#{MAX_RSS}"
-          Sidekiq.logger.warn "this thread will shut down PID #{Process.pid} - Worker #{worker.class} - JID-#{job['jid']}"\
+          Sidekiq.logger.warn "this thread will shut down PID #{Process.pid} - Worker #{worker.class} - JID-#{job['jid']} "\
             "in #{GRACE_TIME} seconds"
           sleep(GRACE_TIME)