16.0.4.0: [FIX] website: stop showing CSS variable assertion tour step to users

Commit [1] introduced a website tour util to assert the value of a CSS
variable. This was used at the start of theme tours to check we are in
fact on the right theme before starting the tour.

While it's great for those tours when they are started as a test, it was
not meant to be shown to users following that tour. This commit fixes
that. Notice that theme tours are currently broken so the issue was
probably hidden. Those will be fixed at [2].

[1]: https://github.com/odoo/odoo/commit/b29e17765f4e912b2dd472493b5be500b3a32c87
[2]: https://github.com/odoo/odoo/pull/106703

Related to task-3084175

closes odoo/odoo#106725

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