Use rubocop-rails >= 2.22.0 for better Rails 7.1 support

Before, rubocop-rails treated the Rails 7.1 `Rails.env.local?` as an
unrecognized environment name, requiring custom configuration of
`Rails/UnknownEnv` as a workaround.

Now that rubocop-rails 2.22.0 is released, this workaround is no longer
needed.

This commit removes the workaround and ensures that `rubocop-rails` is
added to the Gemfile with the `>= 2.22.0` version requirement.

lib/nextgen/generators/rubocop.rb

@@ -6,7 +6,8 @@
 plugins << "minitest" if minitest?
 plugins << "performance"
 plugins << "rails"
-install_gems "rubocop", *plugins.map { "rubocop-#{_1}" }, group: :development, require: false
+install_gem("rubocop-rails", version: ">= 2.22.0", group: :development, require: false)
+install_gems(*plugins.map { "rubocop-#{_1}" }, "rubocop", group: :development, require: false)
 binstub "rubocop"
 
 say_git "Generate .rubocop.yml"

template/.rubocop.yml.tt

@@ -190,15 +190,6 @@ Rails/RootPathnameMethods:
 Rails/SkipsModelValidations:
   Enabled: false
 
-<% if Gem::Version.new(Rails.version) >= Gem::Version.new("7.1.0.beta1") -%>
-Rails/UnknownEnv:
-  Environments:
-    - development
-    - test
-    - production
-    - local
-<% end -%>
-
 Rails/Validation:
   Enabled: false
 

test/nextgen/generators/rubocop_test.rb

@@ -0,0 +1,35 @@
+require_relative "test_case"
+
+class Nextgen::Generators::RubocopTest < Nextgen::Generators::TestCase
+  destination File.join(Dir.tmpdir, "test_#{SecureRandom.hex(8)}")
+  setup :prepare_destination
+
+  setup do
+    %w[README.md Rakefile].each { FileUtils.touch Pathname.new(destination_root).join(_1) }
+    Pathname.new(destination_root).join("Gemfile").write(<<~GEMFILE)
+      source "https://rubygems.org"
+    GEMFILE
+  end
+
+  test "installs rubocop gems in development group, with version spec for rubocop-rails" do
+    apply_generator
+
+    assert_file "Gemfile", /#{Regexp.quote(<<~GEMFILE)}/
+      group :development do
+        gem "rubocop", require: false
+        gem "rubocop-performance", require: false
+        gem "rubocop-rails", ">= 2.22.0", require: false
+      end
+    GEMFILE
+  end
+
+  test "installs generates a .rubocop.yml file that requires additional plugins" do
+    apply_generator
+
+    assert_file ".rubocop.yml", /#{Regexp.quote(<<~YML)}/
+      require:
+        - rubocop-performance
+        - rubocop-rails
+    YML
+  end
+end