[FIX] website: always update color previews after bundle reloads

Before this commit, updating the color previews in the editor panel was
only done if the user remained in the "Theme" tab.

This means that those steps worked:

- Add a snippet in your page
- Go to the theme "tab"
- Change a theme color: validate the color you chose by closing the
  dropdown by clicking inside the theme panel, staying in the theme tab
- Click on the snippet
- Open the background option colorpicker -> theme colors are right

But those apparently same steps did not work:

- Add a snippet in your page
- Go to the theme "tab"
- Change a theme color: validate the color you chose by indirectly
  closing the dropdown by directly clicking on the snippet you added
- Open the background option colorpicker -> theme colors are wrong

task-3419142

closes odoo/odoo#128260

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