Use the correct command name in ovn-nbctl --help

Command to remove the chassis from a ha chassis group is
"ha-chassis-group-remove-chassis". Use the correct function name in
"ovn-nbctl --help".

Reported-at: ovn-org#58
Submitted-at: ovn-org#59
Signed-off-by: Kai Li <likailichee@gmail.com>
Signed-off-by: Numan Siddique <numans@ovn.org>

AUTHORS.rst

@@ -202,6 +202,7 @@ Jun Nakajima                       jun.nakajima@intel.com
 JunhanYan                          juyan@redhat.com
 JunoZhu                            zhunatuzi@gmail.com
 Justin Pettit                      jpettit@ovn.org
+Kai Li                             likailichee@gmail.com
 Kaige Fu                           fukaige@huawei.com
 Keith Amidon
 Ken Ajiro                          ajiro@mxw.nes.nec.co.jp

utilities/ovn-nbctl.c

@@ -768,7 +768,7 @@ HA chassis group commands:\n\
   ha-chassis-group-list     List the HA chassis groups\n\
   ha-chassis-group-add-chassis GRP CHASSIS [PRIORITY] Adds an HA\
 chassis with optional PRIORITY to the HA chassis group GRP\n\
-  ha-chassis-group-del-chassis GRP CHASSIS Deletes the HA chassis\
+  ha-chassis-group-remove-chassis GRP CHASSIS Removes the HA chassis\
 CHASSIS from the HA chassis group GRP\n\
 \n\
 %s\