Indicate that expand_number is case-insensitive.

Reviewed by:	-scsi

lib/libutil/expand_number.3

@@ -51,12 +51,13 @@ argument.
 The
 .Fn expand_number
 function
+is case-insensitive and
 follows the SI power of two convention.
 .Pp
 The prefixes are:
 .Bl -column "Prefix" "Description" "1000000000000000000" -offset indent
 .It Sy "Prefix" Ta Sy "Description" Ta Sy "Multiplier"
-.It Li k Ta No kilo Ta 1024
+.It Li K Ta No kilo Ta 1024
 .It Li M Ta No mega Ta 1048576
 .It Li G Ta No giga Ta 1073741824
 .It Li T Ta No tera Ta 1099511627776