[FIX] website: prevent website info page to crash if view deleted

The website info page was introduced with [1] where the code was
apparently checking for the existence of the view (to be rendered) to be
able to handle a proper error if it did not exists.
It seems like it was to support the case where someone would delete this
view to not leak any info on the public controller. But it's uncertain
as this code is 10 years old.

It was a year later improved with [2] to have an option on the page to
be able to sort of disable it: it would simply show a blank page but it
would still be served.

As of now, the `try/except` with the `get_template()` call is crashing
and rendering traceback whenever this view is deleted, making this code
useless and not doing anything.
It's probably not needed anyway since the option introduced with [2] but
as we are in stable, this commit is making the controller return a
proper 404 page instead of a traceback.
Arguably, that part of the code could be removed. We will do it in the
master forward port.

[1]: https://github.com/odoo/odoo/commit/8aca457e34bdec6257b9bfa917aebe4de053e2aa#diff-d41b2dc5ff6fd6a303373f86e1af97d055db315ccc431749b4ffac1488dea119R145
[2]: https://github.com/odoo/odoo/commit/f025d3e17cbb3b1fd05152ca46af091b6e11ee20

opw-3255831

X-original-commit: e787fef0
Part-of: odoo/odoo#120734