Remove user from collection when leaves

...ts/api/group-chat-msg/server/modifiers/addGroupChatMsg.js

...ts/api/group-chat-msg/server/modifiers/removeGroupChat.js

...imports/api/group-chat/server/methods/destroyGroupChat.js

...5/imports/api/group-chat/server/modifiers/addGroupChat.js

...mports/api/group-chat/server/modifiers/removeGroupChat.js

...-html5/imports/api/meetings/server/handlers/meetingEnd.js

...l5/imports/api/users/server/handlers/presenterAssigned.js

...utton-html5/imports/api/users/server/modifiers/addUser.js

...on-html5/imports/api/users/server/modifiers/removeUser.js

bigbluebutton-html5/imports/api/users/server/publishers.js

bigbluebutton-html5/imports/startup/server/index.js

...button-html5/imports/ui/components/actions-bar/service.js

...tton-html5/imports/ui/components/chat/alert/component.jsx

bigbluebutton-html5/imports/ui/components/chat/container.jsx

bigbluebutton-html5/imports/ui/components/chat/service.js

...tml5/imports/ui/components/poll/live-result/component.jsx

...tml5/imports/ui/components/presentation/cursor/service.js

...uebutton-html5/imports/ui/components/user-list/service.js

...r-participants/user-list-item/user-dropdown/component.jsx

...ton-html5/imports/ui/components/video-provider/service.js