Test failures on cran

https://www.r-project.org/nosvn/R.check/r-devel-linux-x86_64-fedora-gcc/mlr3pipelines-00check.html > ``` > ── Failure ('test_pipeop_learnercv.R:124:3'): PipeOpLearnerCV - cv ensemble averages fold learners ── > Expected `all.equal(object, expected, check.environment = FALSE, ...)` to be TRUE. > Differences: > `actual` is a character vector ('4 string mismatches') > `expected` is a logical vector (TRUE) > > Backtrace: > ▆ > 1. └─global expect_equal(as.character(result_response), task$class_names[max.col(manual_prob)]) at test_pipeop_learnercv.R:124:3 > 2. └─testthat::expect_true(...) > ``` https://github.com/mlr-org/mlr3pipelines/blob/cb8265b72a981fc17689ceb500a7ad97f4d5a53d/tests/testthat/test_pipeop_learnercv.R#L124-L127