chore: bump up iavl

[jinsan-line]

Description

Related w/: Finschia/ostracon#228, Finschia/iavl#18

• To tidy up go.sum, bump up iavl.

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #157 (856c857) into v2/develop (1f739c5) will decrease coverage by 1.78%.
The diff coverage is 67.72%.

@@              Coverage Diff               @@
##           v2/develop     #157      +/-   ##
==============================================
- Coverage       54.99%   53.21%   -1.79%     
==============================================
  Files             812      704     -108     
  Lines           51487    46974    -4513     
==============================================
- Hits            28317    24998    -3319     
+ Misses          20211    19431     -780     
+ Partials         2959     2545     -414     

Impacted Files	Coverage Δ
client/grpc/tmservice/query.pb.gw.go	30.06% <ø> (ø)
client/keys/root.go	100.00% <ø> (ø)
client/keys/utils.go	35.29% <ø> (-3.60%)	⬇️
client/utils.go	44.82% <0.00%> (-1.61%)	⬇️
crypto/armor.go	85.89% <ø> (ø)
crypto/keys/ed25519/ed25519.go	67.34% <ø> (ø)
crypto/keys/multisig/codec.go	100.00% <ø> (ø)
crypto/keys/secp256k1/secp256k1.go	86.79% <ø> (ø)
simapp/test_helpers.go	0.49% <0.00%> (-0.01%)	⬇️
types/address.go	65.71% <ø> (ø)
... and 69 more