Fix margins in showControls=false url param mode

[toger5]

Test:

• add showControls=false&header=none to the url params
• start a call with this netlify build vs call.element.dev

before:

after:

Pulled out of #3638

[robintown]

What do you consider broken about the current margins with controls hidden? This is what I see:

I'm not sure that we should make the footer take up as much empty space in this mode as it does normally, if the flag is for minimizing extra UI elements.

[toger5]

This is what I see.
This is fairly old code I did not want to lose. I was not fully aware of the context when opening the PR.
Its about showControls=false&header=none
then it looks like this:

[toger5]

@robintown updated the impl. It does not work like this anymore due to the footer.hidden
(as i said really old code ;) )

[toger5]

This can get squashed merged.