Relax required_ruby_version to support Ruby 4.0 (#21)

* CI: Add Ruby 3.2 - 3.4 to CI Matrix

Bump actions/checkout from 4 to 6

* Relax `required_ruby_version` to support Ruby 4.0

Add Ruby 4.0 to CI Matrix
Remove the `'bundler', '~> 2.0'` dependency for development

Author: taketo1113

.github/workflows/ci.yml

@@ -9,7 +9,7 @@ jobs:
   rubocop:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: rm .ruby-version
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
@@ -26,9 +26,9 @@ jobs:
       matrix:
         ## Due to https://github.com/actions/runner/issues/849,
         ## we have to use quotes for '3.0'
-        ruby: ['2.4', '2.5', '2.6', '2.7', '3.0', '3.1']
+        ruby: ['2.4', '2.5', '2.6', '2.7', '3.0', '3.1', '3.2', '3.3', '3.4', '4.0']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:

Gemfile

@@ -5,7 +5,6 @@ source 'https://rubygems.org'
 gemspec
 
 group :development, :test do
-  gem 'bundler', '~> 2.0'
   gem 'faraday', '>= 1.0'
   gem 'multipart-parser'
   gem 'rake', '~> 13.0'

faraday-multipart.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |spec|
 
   spec.files = Dir['lib/**/*', 'README.md', 'LICENSE.md', 'CHANGELOG.md']
 
-  spec.required_ruby_version = '>= 2.4', '< 4'
+  spec.required_ruby_version = '>= 2.4'
 
   spec.add_dependency 'multipart-post', '~> 2.0'
 end