qga: Rephrase return docs to avoid type name

qga: Rephrase return docs to avoid type name

"Returns: <description>" is rendered like

    Return: <Type> – <description>

Mentioning the type in the description again is commonly redundant.
There is just one such description.  Rephrase it not to mention the
type.

We did this for qapi/ in commit f7296f8de5c (qapi: rephrase return
docs to avoid type name).

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250717115246.3830007-4-armbru@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>