Update iavl with WorkingHash fix (backport #1484)

[mergify]

Changelist

WorkingHash was computed incorrectly for trees that are initialized with an InitialVersion. This happens when a new store is introduced in an upgrade. If the store is empty, the hash ends up being the same anyways so the bug only manifests when the store has values at the upgrade height.

See dydxprotocol/iavl@1c8b8e7.

Test Plan

[Describe how this PR was tested (if applicable)]

Author/Reviewer Checklist

• If this PR has changes that result in a different app state given the same prior state and transaction list, manually add the state-breaking label.
• If the PR has breaking postgres changes to the indexer add the indexer-postgres-breaking label.
• If this PR isn't state-breaking but has changes that modify behavior in PrepareProposal or ProcessProposal, manually add the label proposal-breaking.
• If this PR is one of many that implement a specific feature, manually label them all feature:[feature-name].
• If you wish to for mergify-bot to automatically create a PR to backport your change to a release branch, manually add the label backport/[branch-name].
• Manually add any of the following labels: refactor, chore, bug.

---

This is an automatic backport of pull request #1484 done by [Mergify](https://mergify.com).