Update I18n to 1.9 (#36564).

git-svn-id: http://svn.redmine.org/redmine/trunk@21400 e93f8b46-1217-0410-a6f0-8f06a7374b81

Author: vividtone

Gemfile

@@ -14,7 +14,7 @@ gem 'marcel'
 gem "mail", "~> 2.7.1"
 gem 'csv', '~> 3.2.0'
 gem 'nokogiri', (Gem.ruby_version < Gem::Version.new('2.6.0') ? '~> 1.12.2' : '~> 1.13.0')
-gem 'i18n', '~> 1.8.2'
+gem 'i18n', '~> 1.9.1'
 gem "rbpdf", "~> 1.20.0"
 gem 'addressable'
 gem 'rubyzip', '~> 2.3.0'