Disambiguate reference to kibibytes, not kilobytes

A minor nitpick that is kind of obvious based on the surrounding context
and reference to powers of two. It's better to be explicit, though.

Signed-off-by: Simon Howard <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>

Author: fragglet

man/man7/zfsprops.7

@@ -543,8 +543,8 @@ cannot be changed once the volume has been written, so it should be set at
 volume creation time.
 The default
 .Sy blocksize
-for volumes is 16 Kbytes.
-Any power of 2 from 512 bytes to 128 Kbytes is valid.
+for volumes is 16 KiB.
+Any power of 2 from 512 bytes to 128 KiB is valid.
 .Pp
 This property can also be referred to by its shortened column name,
 .Sy volblock .