test(e2e): improve waiting after deleting of meeting

When working on https://git.opentalk.dev/opentalk/qa/reports/-/issues/192 I found that the deletion of meetings would not always work. The issue was that the step would not wait long enough for the page to update. After deleting one meeting deleteAllCreatedMeetings might still see the elements and try to delete again and that of course would fail. This MR does two things:

1. puts all things to be waited for into on await Promise.all
2. waits till the specific button (located by the link) is not visible anymore