The livechat button was disabled in website preview because
its implementation could not properly handle being in an iframe
inside the backend [1].
With the public livechat code being refactored to use discuss code,
this is no longer a problem, so the livechat button can be present
again. This also makes previewing the website more correct: the
livechat button is actual present on the website, so hiding it was
a lie.
By re-enabling the livechat button, this also allow to remove the
test coverage by a tour, which was sometimes failing on runbot due
to tour being small and doing `im_livechat/init` rpc after the end
of the tour.
[1]: https://github.com/odoo/odoo/commit/e86c1ce94a148745d58ac38e408e1bc947978670
runbot-24631
closesodoo/odoo#135913
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>
Alexandre Kühn
c191f94b43