[selenium] Remove some useless tests

I dont think that it makes much sense to keep these tests. When
the UI does not fire up at all, all other tests should fail as
well.

Testing if different configuration leads to different UI also does
not make much sense, since this should be covered by backend tests
already.

Bug: T282935
Change-Id: I3549916348bd6785ffb58cfcd20a6d85f4d66d61