Bump unicorn from 5.3.0 to 5.5.3

Bumps [unicorn](https://yhbt.net/unicorn/) from 5.3.0 to 5.5.3.

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Gemfile

@@ -66,7 +66,7 @@ group :development, :test do
   gem 'simplecov', '~> 0.14.1'
   gem 'rubocop', '0.58.2', require: false
   gem 'rubocop-rspec', '1.15.1'
-  gem 'unicorn', '~> 5.3.0'
+  gem 'unicorn', '~> 5.5.3'
   gem 'rspec_junit_formatter', '~> 0.2.3'
   gem 'poltergeist', '1.15.0'
   gem 'timecop'

Gemfile.lock

@@ -209,7 +209,7 @@ GEM
     kaminari (0.15.1)
       actionpack (>= 3.0.0)
       activesupport (>= 3.0.0)
-    kgio (2.11.0)
+    kgio (2.11.3)
     launchy (2.4.3)
       addressable (~> 2.3)
     libhoney (1.13.0)
@@ -319,7 +319,7 @@ GEM
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
     rainbow (3.0.0)
-    raindrops (0.18.0)
+    raindrops (0.19.1)
     rake (12.3.3)
     rdf (1.1.1.1)
     rdf-rdfxml (1.0.1)
@@ -438,7 +438,7 @@ GEM
       unf_ext
     unf_ext (0.0.7.6)
     unicode-display_width (1.4.0)
-    unicorn (5.3.0)
+    unicorn (5.5.3)
       kgio (~> 2.6)
       raindrops (~> 0.7)
     warden (1.2.6)
@@ -512,7 +512,7 @@ DEPENDENCIES
   sprockets (~> 2.12.4)
   timecop
   uglifier (~> 3.2.0)
-  unicorn (~> 5.3.0)
+  unicorn (~> 5.5.3)
   whenever
 
 BUNDLED WITH