Remove unicode gem for Ruby 2.4+

Ideally we wouldn't have Ruby version conditionals in the Gemfile as
this will result in the lock file have uncommited changes by considering
we've already announced we're dropping support for 2.3 [1] I doubt this
will ever be an issue.

[1] https://github.com/mysociety/alaveteli/blob/0.38.0.0/doc/CHANGES.md#upgrade-notes

Gemfile

@@ -144,7 +144,7 @@ gem 'gettext', '< 3.3.0'
 gem 'globalize', rails_upgrade? ? '~> 5.3.0' : '~> 5.2.0'
 gem 'locale', '~> 2.1.3'
 gem 'routing-filter', '~> 0.6.2'
-gem 'unicode', '~> 0.4.4'
+gem('unicode', '~> 0.4.4') if RUBY_VERSION < '2.4'
 gem 'unidecoder', '~> 1.1.0'
 gem 'money', '~> 6.13.8'
 

Gemfile.lock

@@ -378,7 +378,6 @@ GEM
       thread_safe (~> 0.1)
     uglifier (4.2.0)
       execjs (>= 0.3.0, < 3)
-    unicode (0.4.4.4)
     unicode-display_width (1.7.0)
     unidecoder (1.1.2)
     uniform_notifier (1.13.0)
@@ -481,7 +480,6 @@ DEPENDENCIES
   therubyracer (~> 0.12.0)
   thin (~> 1.7.2)
   uglifier (~> 4.2.0)
-  unicode (~> 0.4.4)
   unidecoder (~> 1.1.0)
   vpim (~> 13.11.11)
   web-console (>= 3.3.0)

Gemfile.rails_next.lock

@@ -393,7 +393,6 @@ GEM
       thread_safe (~> 0.1)
     uglifier (4.2.0)
       execjs (>= 0.3.0, < 3)
-    unicode (0.4.4.4)
     unicode-display_width (1.7.0)
     unidecoder (1.1.2)
     uniform_notifier (1.13.0)
@@ -497,7 +496,6 @@ DEPENDENCIES
   therubyracer (~> 0.12.0)
   thin (~> 1.7.2)
   uglifier (~> 4.2.0)
-  unicode (~> 0.4.4)
   unidecoder (~> 1.1.0)
   vpim (~> 13.11.11)
   web-console (>= 3.3.0)