Fix typo

[j-svensmark]

I tried adding a documentation label per your contribution guidelines https://github.com/fidelity/mab2rec/blob/47b4ceb99d943cfd6f92f782384b0a7290b78361/CONTRIBUTING.md#how-to-contribute-documentation-fixes, though it appears github requires triage permissions to edit labels https://docs.github.com/en/issues/using-labels-and-milestones-to-track-work/managing-labels#applying-a-label

[skadio]

@j-svensmark thank you for the fix! Perfect new year’s gift :)