Only check for refseq_select_prot blast db species compatibility if ref proteome similarity step is run with blast

[susannasiebert]

Running the reference proteome similarity step with non-human/mouse species and a reference proteome (peptide) fasta file would always fail the validation on the refseq_select_proteome and species compatibility. The refseq_select_proteome argument has a default so it's always set even if we run with a peptide fasta and not blast.