qapi: Fix argument documentation markup

Member / argument documentation of BlockdevAmendOptionsQcow2,
job-resume, and RDMA_GID_STATUS_CHANGED is parsed as ordinary text due
to missing colon or space before the colon.  The generated
documentation shows these members / arguments as "Not documented".

The fix is obvious: add missing colons, delete extra spaces.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230425064223.820979-13-armbru@redhat.com>