Bump minimum required Ruby version to 3.1

Previous minimum was 2.7, which was end-of-life (EOL) 2023-03-31. 3.0
was EOL 2024-04-23 ([source][]).

[source]: https://www.ruby-lang.org/en/downloads/branches/

Author: dandorman

.github/workflows/ci.yml

@@ -17,8 +17,6 @@ jobs:
     strategy:
       matrix:
         ruby:
-          - '2.7'
-          - '3.0'
           - '3.1'
           - '3.2'
     steps:

workos.gemspec

@@ -30,5 +30,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'vcr', '~> 5.0.0'
   spec.add_development_dependency 'webmock'
 
-  spec.required_ruby_version = '>= 2.7'
+  spec.required_ruby_version = '>= 3.1'
 end