Tor Browser's letterboxing wastes too much screen space in some cases

Hi there,

the letterboxing feature was introduced a month ago in Tails, and in some cases an important part of the screen is wasted, as you can see here:

(see the margin at the bottom)

It would be great to reconsider default dimensions (see #30556 (closed)) or to allow one-click opt-out

Thanks for your highly valuable work!