fix(deps): update module github.com/cosmos/iavl to v0.21.1

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
github.com/cosmos/iavl	v0.20.0 -> v0.21.1

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Release Notes

cosmos/iavl (github.com/cosmos/iavl)

### [`v0.21.1`](https://redirect.github.com/cosmos/iavl/compare/v0.21.0...v0.21.1) [Compare Source](https://redirect.github.com/cosmos/iavl/compare/v0.21.0...v0.21.1) ### [`v0.21.0`](https://redirect.github.com/cosmos/iavl/compare/v0.20.1...v0.21.0) [Compare Source](https://redirect.github.com/cosmos/iavl/compare/v0.20.1...v0.21.0) ### [`v0.20.1`](https://redirect.github.com/cosmos/iavl/releases/tag/v0.20.1) [Compare Source](https://redirect.github.com/cosmos/iavl/compare/v0.20.0...v0.20.1) #### 0.20.1 (September 5, 2023) ##### Improvements - [#​654](https://redirect.github.com/cosmos/iavl/pull/654) Add API `TraverseStateChanges` to extract state changes from iavl versions. - [#​726](https://redirect.github.com/cosmos/iavl/pull/726) Make `KVPair` and `ChangeSet` serializable with protobuf. - [#​795](https://redirect.github.com/cosmos/iavl/pull/795) Use gogofaster buf plugin. ##### Bug Fixes - [#​801](https://redirect.github.com/cosmos/iavl/pull/801) Fix rootKey empty check by len equals 0. - [#​829](https://redirect.github.com/cosmos/iavl/pull/829) Fix fastnode concurrency panic. **Full Changelog**: https://github.com/cosmos/iavl/compare/v0.20.0...v0.20.1

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[renovate[bot]]

ℹ Artifact update notice

File name: go.mod

In order to perform the update(s) described in the table above, Renovate ran the go get command, which resulted in the following additional change(s):

• 1 additional dependency was updated

Details:

Package	Change
gopkg.in/check.v1	v1.0.0-20200902074654-038fdea0a05b -> v1.0.0-20201130134442-10cb98267c6c