Fix read_group ability

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/ability.rb

@@ -184,7 +184,7 @@ class Ability
     def group_abilities user, group
       rules = []
 
-      if user.admin? || Projects::CollectService.new.execute(user, group: group).any?
+      if user.admin? || group.users.include?(user) || Projects::CollectService.new.execute(user, group: group).any?
         rules << :read_group
       end