Exclude vanished players from tab complete list

Part 2 of fixing #1745

src/main/java/com/gmail/nossr50/commands/database/McremoveCommand.java

@@ -45,7 +45,7 @@ public class McremoveCommand implements TabExecutor {
     public List<String> onTabComplete(CommandSender sender, Command command, String alias, String[] args) {
         switch (args.length) {
             case 1:
-                Set<String> playerNames = UserManager.getPlayerNames();
+                List<String> playerNames = CommandUtils.getOnlinePlayerNames(sender);
                 return StringUtil.copyPartialMatches(args[0], playerNames, new ArrayList<String>(playerNames.size()));
             default:
                 return ImmutableList.of();