Skip tests that require 5.43 if not on 5.43
It'll be another month of red X's if these tests keep running on <5.43 so this will make it easier to see actual fails.
There is also a separate problem because there's a gap right now between 5.42 which is released, but 5.43 is still in alpha not beta yet so it can't find a current RC to download, but that should change in a day or two.