Fix `exon` redux for 2 field alleles

To correctly reduce to the exon version, it first expands to W and then reduce to exon level producing all possibilities at exon level.

Fixes #320

What's Changed

• Bump gunicorn from 20.1.0 to 22.0.0 by @dependabot in #319
• Fix exon reductions for 2 field alleles by @pbashyal-nmdp in #322

Full Changelog: 1.1.2...1.1.3