Drop Ruby 3.1 support (#76)

Noticed while updating dependencies:

```
activesupport-8.0.1 requires ruby version >= 3.2.0, which is incompatible with the current version, 3.1.6
```

Ruby 3.1 is in security maintenance phase and will be EOL'ed soon (31
March 2025). Seems sensible enough to go ahead and drop it here and bump
this gem to v4.0.0.

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       fail-fast: false
       matrix:
         gemfile: [Gemfile, gemfiles/minimum_dependencies.gemfile]
-        ruby: [3.1, 3.2, 3.3, 3.4]
+        ruby: [3.2, 3.3, 3.4]
     steps:
       - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1

.github/workflows/publish.yml

@@ -20,7 +20,7 @@ jobs:
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true
-          ruby-version: 3.1
+          ruby-version: 3.2
       - uses: rubygems/release-gem@v1
         with:
           await-release: false
@@ -36,7 +36,7 @@ jobs:
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true
-          ruby-version: 3.1
+          ruby-version: 3.2
       - run: |
           mkdir -p $HOME/.gem
           touch $HOME/.gem/credentials

.rubocop.yml

@@ -3,7 +3,7 @@ inherit_from: config/default.yml
 require: rubocop-packaging
 
 AllCops:
-  TargetRubyVersion: 3.1
+  TargetRubyVersion: 3.2
 
 Naming/FileName:
   Exclude:

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    rubocop-cargosense (3.1.0)
+    rubocop-cargosense (4.0.0)
       rubocop (~> 1.64)
       rubocop-capybara (~> 2.20)
       rubocop-factory_bot (~> 2.26, >= 2.26.1)

rubocop-cargosense.gemspec

@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
 Gem::Specification.new do |spec|
-  spec.required_ruby_version = ">= 3.1"
+  spec.required_ruby_version = ">= 3.2"
 
   spec.name          = "rubocop-cargosense"
-  spec.version       = "3.1.0"
+  spec.version       = "4.0.0"
   spec.authors       = ["CargoSense"]
   spec.email         = ["rubygems@cargosense.com"]