remove `"auto"` and `"cor_auto"` from `dynEGA`

[AlexChristensen]

Since dynEGA computes the derivatives of the time series, all values (even categorical) will be continuous.

It is possible for there to be 7 or fewer continuous values resulting in "auto" and "cor_auto" to default to categorical correlations (polychoric/tetrachoric/polyserial/biserial). For "auto", a range error will be thrown in polychoric.matrix if derivative values are less than 0

A workaround for now is to use corr = "pearson" or corr = "spearman"

Once fixed, only "pearson" and "spearman" will be available by default

[AlexChristensen]

Resolution: treat continuous data with fewer categories than ordinal.categories as categorical