Fix the name of the zfs_prefetch_disable parameter (openzfs#16319)

The ZFS module parameter name is zfs_prefetch_disable, not
zfs_disable_prefetch.

Signed-off-by: Peter Doherty <peterd@acranox.org>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>

man/man7/zfsprops.7

@@ -1639,7 +1639,7 @@ then only metadata are prefetched.
 The default value is
 .Sy all .
 .Pp
-Please note that the module parameter zfs_disable_prefetch=1 can
+Please note that the module parameter zfs_prefetch_disable=1 can
 be used to totally disable speculative prefetch, bypassing anything
 this property does.
 .It Sy setuid Ns = Ns Sy on Ns | Ns Sy off