bump required version of ruby to match our matrix

Author: jhongturney

octocatalog-diff.gemspec

@@ -3,7 +3,7 @@ require 'json'
 DEFAULT_PUPPET_VERSION = '5.5.22'.freeze
 
 Gem::Specification.new do |s|
-  s.required_ruby_version = '>= 2.0.0'
+  s.required_ruby_version = '>= 2.6.0'
 
   s.name        = 'octocatalog-diff'
   s.version     = ENV['OCTOCATALOG_DIFF_VERSION'] || File.read(File.join(File.dirname(__FILE__), '.version')).strip