[FIX] web_editor: non-uniform behaviour in

Before this commit:

When a new list is created and any list item is applied a style
like h1, bold ,itallic etc.. and when when toggle that list, the list
style breaks

After this commit:

Toggling through the list does not break the style.

closes odoo/odoo#119012

Task-id: 3269908
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>