docs: Move licence/copyright from HTML output to rST comments

docs: Move licence/copyright from HTML output to rST comments

Our built HTML documentation now has a standard footer which
gives the license for QEMU (and its documentation as a whole).
In almost all pages, we either don't bother to state the
copyright/license for the individual rST sources, or we put
it in an rST comment. There are just three pages which render
copyright or license information into the user-visible HTML.

Quoting a specific (different) license for an individual HTML
page within the manual is confusing. Downgrade the license
and copyright info to a comment within the rST source, bringing
these pages in line with the rest of our documents.

Suggested-by: Markus Armbruster <[email protected]>
Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Marc-André Lureau <[email protected]>
Reviewed-by: Cleber Rosa <[email protected]>
Reviewed-by: Markus Armbruster <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Message-id: 20210722192016[email protected]