dep: set required_ruby_version to ">= 2.5.0"

this matches the oldest version of Rails (6.0/6.1)

Author: flavorjones

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["2.2", "2.3", "2.4", "2.5", "2.6", "2.7", "3.0", "3.1", "3.2", "ruby-head", "truffleruby-head"]
+        ruby: ["2.5", "2.6", "2.7", "3.0", "3.1", "3.2", "ruby-head", "truffleruby-head"]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
@@ -51,7 +51,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["jruby-9.2", "jruby-9.3", "jruby-head"]
+        ruby: ["jruby-9.3", "jruby-9.4", "jruby-head"]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3

rails-html-sanitizer.gemspec

@@ -13,6 +13,8 @@ Gem::Specification.new do |spec|
   spec.homepage      = "https://github.com/rails/rails-html-sanitizer"
   spec.license       = "MIT"
 
+  spec.required_ruby_version = ">= 2.5.0"
+
   spec.metadata      = {
     "bug_tracker_uri"   => "https://github.com/rails/rails-html-sanitizer/issues",
     "changelog_uri"     => "https://github.com/rails/rails-html-sanitizer/blob/v#{spec.version}/CHANGELOG.md",