Bump up cosmjs 0.31.0

[loin3]

Summary

Bump up cosmjs 0.31.0 and we can delete lots of modules in finsciha-js/finschia/modules.

Problem Definition

Proposal

If cosmjs bumped up to 0.31.0, wasm module in finschia-js/finschja/modules can be deleted because the things changed in cosmjs are PR'd from finschia-js

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