[FIX] website: fix / optimize canonical url

Homepage was never considered as canonical due to the trailing /
domain.com/fr/ != domain.com/fr

Now _get_canonical_url_localized for homepage is fixed.

Remove all computation related to canonical that is usless for connected
user. It is mainly used for SEO tools/bots/crawler.

Initially planed for 13.0 with [1] but reverted with [2].

[1]: https://github.com/odoo/odoo/commit/33167b3928c767a08fdc7eedc3e6204aac9cac08
[2]: https://github.com/odoo/odoo/commit/deb23450f18196c7f8d9e819db603fccd407b82a



closes odoo/odoo#93191

Signed-off-by: Romain Derie (rde) <rde@odoo.com>