include/block/block.h: drop non-ascii quotation mark

This is the only non-ascii character in the file and it doesn't really
needed here. Let's use normal "'" symbol for consistency with the rest
11 occurrences of "'" in the file.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
1 file changed