Update a comment to match the code

GRUB supports large_blocks.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Laager <rlaager@wiktel.com>
Closes #8626

module/zfs/spa.c

@@ -612,8 +612,8 @@ spa_prop_validate(spa_t *spa, nvlist_t *props)
 				/*
 				 * Must be ZPL, and its property settings
 				 * must be supported by GRUB (compression
-				 * is not gzip, and large blocks or large
-				 * dnodes are not used).
+				 * is not gzip, and large dnodes are not
+				 * used).
 				 */
 
 				if (dmu_objset_type(os) != DMU_OST_ZFS) {