The stacks tuning tests are taking too long

[EmilHvitfeldt]

File: https://github.com/tidymodels/extratests/blob/main/tests/testthat/test-stacks-tuning.R

[simonpcouch]

The neural network and nearest neighbors models take much longer than the others:

i 1 of 6 tuning:     rec_lr
✔ 1 of 6 tuning:     rec_lr (1.7s)
i 2 of 6 tuning:     rec_bt
i Creating pre-processing data to finalize unknown parameter: mtry
✔ 2 of 6 tuning:     rec_bt (2.8s)
i 3 of 6 tuning:     rec_dt
✔ 3 of 6 tuning:     rec_dt (5.5s)
i 4 of 6 tuning:     rec_svm
✔ 4 of 6 tuning:     rec_svm (1.5s)
i 5 of 6 tuning:     rec_nn
✔ 5 of 6 tuning:     rec_nn (12.4s)
i 6 of 6 tuning:     rec_knn
✔ 6 of 6 tuning:     rec_knn (13.1s)

[simonpcouch]

Ah, closed in #203.