[FIX] survey: remove navbar in survey mode

Steps to reproduce:

  - Install `survey` module
  - Go to survey and open any survey
  - Click on 'Test' button

Issue:

  Navbar is visible in survey mode (and therefore able to edit the
  survey with web editor).

Cause:

  At some point, the XML has been refractored and the concerned `nav`
  element as been replaced by a `div` element, but the related CSS that
  hide the navbar has not been updated.

opw-3369894

closes odoo/odoo#148569

X-original-commit: bd91a88c68c5fb4903791eee1cbb822198d79ca0
Signed-off-by: David Beguin (dbe) <dbe@odoo.com>
Signed-off-by: Nasreddin Boulif (bon) <bon@odoo.com>

addons/survey/static/src/scss/survey_templates_form.scss

@@ -4,7 +4,7 @@
   only for this.
   TODO: SmartPeople Fixme - cleaner solution? be my guest!
  **********************************************************/
-nav.o_frontend_to_backend_nav {
+div.o_frontend_to_backend_nav {
     display: none !important;
 }