error in `extract` code for test objects

[simonpcouch]

Before https://github.com/tidymodels/tune/pull/575, failing extract code used to raise no prompts to the user. The test objects try to tidy kknn objects in extract code and result in errors. They're now surfaced effectively and don't seem to cause issues with tests downstream, but may be worth cleaning up regardless.

mt_spln_knn_bo_sep <-
 tune_bayes(knn_mod_two,
            spline_rec,
            resamples = folds,
            iter = 3,
            control = b_ctrl)
#> → A | error:   No tidy method for objects of class train.kknn