Remove Fixme comment in queue

[s3bw]

There is a //FIXME comment in the queuelinkedlist.go that should be resolved.

See: https://github.com/maximelamure/algorithms/blob/master/datastructure/queuelinkedlist.go#L43

[maximelamure]

What do you suggest to fix it? Do you want to return an error if the queue is empty?