[#2878] Improved note

Author: fxdupont

doc/sphinx/arm/hooks-host-cmds.rst

@@ -276,7 +276,7 @@ run in read-only mode.
    Since kea version 2.7.0 an empty reservation is implicitly global, i.e.
    if no ``subnet-id`` entry is present and for DHCPv4 ``ip-address`` or
    for DHCPv6 ``ip-addresses`` and ``prefixes`` do not specify a reserved
-   address or prefix the command is valid and adds a global (subnet id 0)
+   address or prefix the command is valid and adds a global (subnet-id 0)
    host reservation.
 
 .. isccmd:: reservation-get