dropDown call in user acceptance tests is broken in the vue.js based front-end

As of today, there is a bug on taiko [1] that prevents some user acceptance tests to succeed properly.

The tests we've found so far are selecting the "Most of mi mail is..." option in the registration page.

A workaround for it is provided, but it'll break easily once we add new dropdown menus to other pages.

We should either find an alternative solution for changing such menu, or watch until it's fixed by the Taiko devs.

Such bug was first observed in the MR !362 (merged).