qapi: Reformat recent doc comments to conform to current conventions

Since commit a937b6aa (qapi: Reformat doc comments to conform to
current conventions), a number of comments not conforming to the
current formatting conventions were added.  No problem, just sweep
the entire documentation once more.

To check the generated documentation does not change, I compared the
generated HTML before and after this commit with "wdiff -3".  Finds no
differences.  Comparing with diff is not useful, as the reflown
paragraphs are visible there.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20230720071610.1096458-7-armbru@redhat.com>