refactor: drop support for unmaintained Redmine versions

Author: xel1045

init.rb

@@ -10,7 +10,7 @@
   url 'https://github.com/eXolnet/redmine_changeset_statuses'
   author_url 'https://www.exolnet.com'
 
-  requires_redmine :version_or_higher => '3.4'
+  requires_redmine :version_or_higher => '4.2'
 end
 
 require File.dirname(__FILE__) + '/lib/redmine_changeset_statuses'