Our current XMPP chat rooms lose this information on a weekly basis so
let's not bother with this any more.

Refs: #12456

Fix-committed: #12444

Startmenü is commonly used for MS Windows, and we don't want to confuse
new users.

This wording is easier to understand and refers to the usage of accessibility
in GNOME.

This reverts commit abf0a12b.

This reverts the remaining part of
commit:e54b9f7e, as our website looks ugly with
the breadcrumbs reintroduced if we keep these CSS bits.

refs: #12134

On #11911 it was said "They will be back in January once the donation campaign
is over", but apparently this was forgotten.

Partially reverts e54b9f7e, that did
two (related) things at a time: I've left the responsive header height part in
case it's still useful.

I've find it too hard to guess if this is going to break the test suite,
so let's see.

This reverts commit 6cd48d48.

This reverts commit 2919ff01.