Merge branch 'sh-update-redis' into 'master'

Update Redis gem from 3.1.5 -> 4.1.2

See merge request gitlab-org/gitlab-monitor!99
2 jobs for master in 57 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #5066786
rspec

00:00:57

passed #5066787
rubocop

00:00:54