engine parameters for qrnn

[topepo]

These are not tunable, are they? Since they are listed in the section "Tuning Parameters", it might be good to clarify that they are not tunable.

Originally posted by @hfrick in tidymodels/parsnip#1323 (comment)

[hfrick]

Just commenting to clarify that this issue means we still want to add dials parameters for the engine parameters for qrnn, i.e., it's not a documentation issue (my quoted comment above was referring to the parsnip documentation).