[FIX] website: don't show website info page in sitemap if disabled

There is a historical code to return an error/404 when someone disable
the website info view, see [1].
There is also a feature introduced to add an option to disable the
content of this controller, see [2].
Commit [2] should probably have gotten rid of the view check in [1]
which was probably the way people used to stop this page leaking their
DB information.

From there, regardless if you deleted or disabled the view, the page
would still be referenced in the sitemap.xml, which would lead to a
traceback page (case 1) or a blank page (case 2).

This commit is simply conditionning the presence of this page in the
sitemap so it's removed from it if you disable/remove the website info
view.
It will help SEO wise to not have error page in it.

Note that we probably don't want to keep indexing this page, as it is
a technical link which doesn't bring any value to our clients to be
included in their sitemap.
It might have been useful for Odoo to perform some google search / stats
or something like that.
But since this is a stable fix, the behavior is kept as is as much as
possible.

Also note that it has always been in sitemap, even if marked
excplicitely since [3].

[1]: https://github.com/odoo/odoo/commit/8aca457e34bdec6257b9bfa917aebe4de053e2aa#diff-d41b2dc5ff6fd6a303373f86e1af97d055db315ccc431749b4ffac1488dea119R146-R149
[2]: https://github.com/odoo/odoo/commit/f025d3e17cbb3b1fd05152ca46af091b6e11ee20
[3]: https://github.com/odoo/odoo/commit/e19227d3ba9c9296bfc0c221ac70a863a571b9a6#diff-d41b2dc5ff6fd6a303373f86e1af97d055db315ccc431749b4ffac1488dea119L200



opw-3255831

closes odoo/odoo#120336

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>