parsnip::set_model_arg should be "sample_size" not "sample_prop"

[p-schaefer]

Here:

treesnip/R/lightgbm.R

Line 169 in 60aade5

parsnip = "sample_prop",

and this:

treesnip/R/lightgbm.R

Line 171 in 60aade5

func = list(pkg = "dials", fun = "sample_size"),

should be:
func = list(pkg = "dials", fun = "sample_prop"),