ovn-architecture: update description for OVN RBAC wrt Encap table
Encap table already supported authentication. Update the out-of-date
description.
Acked-by: Mark Michelson
<dt><code>Encap</code></dt>
<dd>
<p>
- <code>Authorization</code>: disabled (all clients are considered
- to be authorized. Future: add a "creating chassis name" column to
- this table and use it for authorization checking.
+ <code>Authorization</code>: client ID must match the chassis name.
</p>
<p>
<code>Insert/Delete</code>: row insertion and row deletion
