sourmash compute nucleotide was getting skipped but not peptide - fix the logic for it

[pranathivemuri]

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• PR is to dev rather than master
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[pranathivemuri]

@olgabot could you please review this PR?

[pranathivemuri]

@olgabot could you please review this PR?

[olgabot]

Thanks for the ping!

[pranathivemuri]

@olgabot since the markdown bits don't completely pass, I can't merge. if you have the rights to merge, could you please?