CLEANUP: sink: remove useless cleanup in sink_new_from_logger()

CLEANUP: sink: remove useless cleanup in sink_new_from_logger()

As reported by Ilya in GH #2994, some cleanup parts in
sink_new_from_logger() function are not used.

We can actually simplify the cleanup logic to remove dead code, let's
do that by renaming "error_final" label to "error" and only making use
of the "error" label, because sink_free() already takes care of proper
cleanup for all sink members.