Upgrade Unicorn to v5.5.1

This upgrade fixes a problem that caused a single listener to monopolize
a Unicorn worker. By default, GitLab Omnibus configures Unicorn to
listen both on a UNIX domain socket and a TCP socket. One of those
sockets can be starved if many requests are queued
(https://yhbt.net/unicorn-public/20200416092457.GA5000@dcvr/).

Full list of changes:
https://github.com/defunkt/unicorn/compare/v5.4.1...v5.5.5

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/213257

Gemfile

@@ -166,7 +166,7 @@ gem 'diff_match_patch', '~> 0.1.0'
 gem 'rack', '~> 2.0.9'
 
 group :unicorn do
-  gem 'unicorn', '~> 5.4.1'
+  gem 'unicorn', '~> 5.5'
   gem 'unicorn-worker-killer', '~> 0.4.4'
 end
 

Gemfile.lock

@@ -589,7 +589,7 @@ GEM
       activerecord
       kaminari-core (= 1.0.1)
     kaminari-core (1.0.1)
-    kgio (2.11.2)
+    kgio (2.11.3)
     knapsack (1.17.0)
       rake
     kramdown (2.1.0)
@@ -1108,7 +1108,7 @@ GEM
     unicode_plot (0.0.4)
       enumerable-statistics (>= 2.0.1)
     unicode_utils (1.4.0)
-    unicorn (5.4.1)
+    unicorn (5.5.5)
       kgio (~> 2.6)
       raindrops (~> 0.7)
     unicorn-worker-killer (0.4.4)
@@ -1410,7 +1410,7 @@ DEPENDENCIES
   u2f (~> 0.2.1)
   uglifier (~> 2.7.2)
   unf (~> 0.1.4)
-  unicorn (~> 5.4.1)
+  unicorn (~> 5.5)
   unicorn-worker-killer (~> 0.4.4)
   unleash (~> 0.1.5)
   validates_hostname (~> 1.0.6)

changelogs/unreleased/sh-upgrade-unicorn.yml

+---
+title: Upgrade Unicorn to v5.5.1
+merge_request: 30541
+author:
+type: fixed