Since we are already iterating the ZAP, we have exact string key to
remove, we do not need to call zap_remove_int() with the int key we
just converted, we can call zap_remove() for the original string.
This should make no functional change, only a micro-optimization.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by: iXsystems, Inc.
Closes#15056