Updating WGS prep files adds "BarcodeSequence", LinkerPrimerSequence" to prep file

[ackermag]

This should not happen with WGS preps.

[ackermag]

It may just be the warning message that needs to be removed - the columns were not downloaded or in the prep info summary page despite the warning

[antgonza]

Qiita no longer automatically produces QIIME1 or merges per preparation sample/prep files; thus, this no longer applies.
Changed implemented in: #3043