doc: note update of Ruby on Rails 6.0 related packages to 6.0.5.1

devel/ruby-activesupport60
devel/ruby-activemodel60
devel/ruby-activejob60
www/ruby-actionview60
www/ruby-actionpack60
databases/ruby-activerecord60
mail/ruby-actionmailer60
devel/ruby-activestorage60
mail/ruby-actionmailbox60
www/ruby-actioncable60
devel/ruby-railties60
textproc/ruby-actiontext60
www/ruby-rails60

(taca)