Update README, update minimum ruby version

Author: hschne

.ruby-version

@@ -1 +1 @@
-3.1.0
+4.0.1

README.md

@@ -79,8 +79,6 @@ query myQuery{
 
 For a showcase of what you can do with `graphql-groups` check out [graphql-groups-demo](https://github.com/hschne/graphql-groups-demo) 
 
-Find a hosted version of the demo app [on Heroku](https://graphql-groups-demo.herokuapp.com/). 
-
 ### Grouping by Multiple Attributes
 
 This library really shines when you want to group by multiple attributes, or otherwise retrieve complex statistical information

graphql-groups.gemspec

@@ -31,7 +31,7 @@ Gem::Specification.new do |spec|
   spec.executables = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = Gem::Requirement.new('>= 3.1.0')
+  spec.required_ruby_version = Gem::Requirement.new('>= 3.3.0')
 
   spec.add_development_dependency 'activerecord', '~> 7.2'
   spec.add_development_dependency 'benchmark-ips', '~> 2.8'