doc: fix spelling

I am pretty sure that's the word Fabrice Bellard intended to write.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

qemu-options.hx

@@ -3015,7 +3015,7 @@ udp::4555@@:4556} to QEMU. Another approach is to use a patched
 version of netcat which can listen to a TCP port and send and receive
 characters via udp.  If you have a patched version of netcat which
 activates telnet remote echo and single char transfer, then you can
-use the following options to step up a netcat redirector to allow
+use the following options to set up a netcat redirector to allow
 telnet on port 5555 to access the QEMU port.
 @table @code
 @item QEMU Options: