Fix trivial typo in zfs-diff.8

Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tamas TEVESZ <[email protected]>
Closes #11268 
Closes #11272

Author: melak

man/man8/zfs-diff.8

@@ -66,7 +66,7 @@ R       The path has been renamed
 .Bl -tag -width "-F"
 .It Fl F
 Display an indication of the type of file, in a manner similar to the
-.Fl
+.Fl F
 option of
 .Xr ls 1 .
 .Bd -literal