docs/proces: branching-checklist: Update the section "add to patchbot"

Make clear the patchbot is accessible from the user "xen" on xenbits.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Henry Wang <Henry.Wang@arm.com>

----
    Changes in v2:
        - Add Henry's reviewed-by
        - Add George's acked-by

docs/process/branching-checklist.txt

@@ -48,7 +48,7 @@ ov=4.0
     git commit -m "cr-for-branches: Add Xen and QEMU $v branch"
 
 * add to patchbot
-    on xenbits
+    ssh xen@xenbits.xen.org
     cd ~/HG/patchbot/
 
     cp xen--master.patchbot-reported-heads xen--stable-$v.patchbot-reported-heads