Remove checks for old Ruby versions

Also:
- Test against JRuby 9.4
- Remove conditional installation of `json` on JRuby, because it appears
  to be part of the standard library on all supported Ruby versions

Note: the minimum required JRuby version appears to be 9.4.6.0

.github/workflows/ruby.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['3.1', '3.2', '3.3']
+        ruby-version: ['3.1', '3.2', '3.3', 'jruby-9.4']
 
     steps:
     - uses: actions/checkout@v4

Gemfile

@@ -2,15 +2,4 @@ source 'https://rubygems.org'
 
 gem 'pry', require: false
 
-# JSON gem no longer supports ruby < 2.0.0
-if defined?(JRUBY_VERSION)
-  gem 'json'
-elsif RUBY_VERSION =~ /^1/
-  # Legacy gem locks for ruby 1.9.x
-  gem 'json',           '~> 1.8.3'
-  gem 'tins',           '~> 1.6.0'
-  gem 'term-ansicolor', '< 1.4'
-end
-gem 'i18n', '<= 1.2.0' if RUBY_VERSION < '2.3'
-
 gemspec

README.md

@@ -40,8 +40,6 @@ A Ruby Library for dealing with money and currency conversion.
 
 - Your app must use UTF-8 to function with this library. There are a
   number of non-ASCII currency attributes.
-- This app requires JSON. If you're using JRuby < 1.7.0
-  you'll need to add `gem "json"` to your Gemfile or similar.
 
 ## Downloading
 
@@ -351,11 +349,11 @@ The following example implements a `Redis` store to save exchange rates to a red
 
 class RedisRateStore
   INDEX_KEY_SEPARATOR = '_TO_'.freeze
-  
+
   # Using second db of the redis instance
   # because sidekiq uses the first db
   REDIS_DATABASE = 1
-  
+
   # Using Hash to store rates data
   REDIS_STORE_KEY = 'rates'
 

money.gemspec

@@ -22,8 +22,8 @@ Gem::Specification.new do |s|
   s.add_development_dependency "rspec", "~> 3.4"
   s.add_development_dependency "yard", "~> 0.9.11"
   s.add_development_dependency "kramdown", "~> 2.3"
-  s.add_development_dependency "rbs" if RUBY_VERSION >= "2.7.0"
-  s.add_development_dependency "typeprof" if RUBY_VERSION >= "2.7.0"
+  s.add_development_dependency "rbs"
+  s.add_development_dependency "typeprof"
 
   s.required_ruby_version = '>= 3.1'