Apply uniqueness check after excluding values

[billdenney]

The "rows that are not unique" test occurs before filtering the data for excluded rows. Sometimes, rows may be excluded because they are duplicates. So, perform the uniqueness test after accounting for exclusion.

https://github.com/billdenney/pknca/blob/7ca2a9333b097c813e839b0206a73c92de670282/R/class-PKNCAconc.R#L109

https://github.com/billdenney/pknca/blob/7ca2a9333b097c813e839b0206a73c92de670282/R/class-PKNCAdose.R#L114