Fix the actions with UnexpectedImprovement(Skip)
The flow about how to interpret a test with the result "UnexpectedImprovement(Skip)" needs to be modified. A previously failing test went to "NotSupported", and that means that it is not failing now. It's enough removing it from fails, with no need to add it to skips.
This comes from the discussion in a uprev Piglit in Mesa
: mesa/mesa!31379 (comment 2600375)