[FIX] website: correctly find the confirm dialog url input value

The clone page behavior in the page properties and the page manager was
changed with [1].
But it was actually not working anymore since [2]  as the input URL
could not be found, so it was crashing (`this.$ does not exist`).

This commit repair that clone page dialog but it is actually only fixing
the consequence of the issue and not the root cause as it should.

A deeper fix fixing the root cause will be done at [3].
In the meantime, this commit will be enough to prevent the issue as we
have more and more opw about that.

[1]: https://github.com/odoo/odoo/commit/4e340cc5f0c1fe9de17a2b852de4faf65a33926a
[2]: https://github.com/odoo/odoo/commit/4b8b079a7d9991a8dc481fe71a45185d672135c9
[3]: https://github.com/odoo/odoo/pull/104220



Courtesy of daramousk for this fix

opw-3033878
opw-3043224
opw-3046485
opw-3042542

closes odoo/odoo#104372

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