Doc: tools: Add COMPAT note for crm_resource --host-uname option

This is a hidden alias for the --node option. It has been hidden since
at least f33d9ee5 (2009), but it was used in resource-agents <v4.2.0
(see resource-agents commit c86b8aed).

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>