readme: fix version since addition of IMAP options
readme: fix version since addition of IMAP options

otsuka512/docker-redmine,vladm/docker-redmine,patope/docker-redmine,ekulos/docker-redmine,otsuka512/docker-redmine,tigerich/docker-redmine,EvgenyKarataev/docker-redmine,hasegaw/docker-redmine,EvgenyKarataev/docker-redmine,sameersbn/docker-redmine,sameersbn/docker-redmine,sameersbn/docker-redmine,joshuacox/docker-redmine,patope/docker-redmine,hasegaw/docker-redmine,ekulos/docker-redmine,joshuacox/docker-redmine,tigerich/docker-redmine,vladm/docker-redmine,otsuka512/docker-redmine