qapi: Don't repeat member type in its documentation text

qapi: Don't repeat member type in its documentation text

Documentation generated for the arguments of MEMORY_FAILURE looks like

    "recipient": "MemoryFailureRecipient"
       recipient is defined as "MemoryFailureRecipient".

    "action": "MemoryFailureAction"
       action that has been taken.  action is defined as
       "MemoryFailureAction".

    "flags": "MemoryFailureFlags"
       flags for MemoryFailureAction.  action is defined as
       "MemoryFailureFlags".

The "action is defined as ..." are redundant.  Drop.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240322140910.328840-10-armbru@redhat.com>