Pipelines autotest does not appear to test some affect_columns behaviour

Apparently some behaviour was only tested by [PipeOpMissInd autotests](https://github.com/mlr-org/mlr3pipelines/blob/f8e8bc02d405c1dd8e28a1ab03c8698d8110b9e2/tests/testthat/test_pipeop_missind.R#L6) because that one has `affect_columns` set by default? See why autotests don't all do this kind of check.