With the BS4 update, a traceback occured when clicking on a m2m tag using colors
in a list view.
When using colors on m2m tags, the badge was wrapped inside a `dropdown-toggle`.
However, there is no `dropdown-menu` by default (it is only rendered in FormFieldMany2ManyTags
when clicking on the `.dropdown-toggle`, hence the traceback.
The `dropdown-toggle` class is now only set if necessary.
Task 1925313
closesodoo/odoo#31445