[FIX] Remove AutoComplete parameters on inviteUsers (RocketChat#14906)

For some reason, when the popupList container already had an item,
its width parameter would be set to a smaller value than the
initial one.
Removing the container selector and the position from
the AutoComplete parameters was a simple way to avoid the container's
width to change after the insertion of the first item.

app/ui-flextab/client/tabs/inviteUsers.js

@@ -138,9 +138,7 @@ Template.inviteUsers.onCreated(function() {
 	this.ac = new AutoComplete({
 		selector: {
 			item: '.rc-popup-list__item',
-			container: '.rc-popup-list__list',
 		},
-		position: 'fixed',
 		limit: 10,
 		inputDelay: 300,
 		rules: [{