build(deps): bump ethers from 5.6.1 to 5.6.4 (#341)

Bumps [ethers](https://github.com/ethers-io/ethers.js/tree/HEAD/packages/ethers) from 5.6.1 to 5.6.4.
- [Release notes](https://github.com/ethers-io/ethers.js/releases)
- [Changelog](https://github.com/ethers-io/ethers.js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ethers-io/ethers.js/commits/v5.6.4/packages/ethers)

---
updated-dependencies:
- dependency-name: ethers
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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package.json

@@ -35,7 +35,7 @@
     "axios": "0.24.0",
     "bignumber.js": "9.0.1",
     "ethereumjs-wallet": "^1.0.2",
-    "ethers": "^5.6.1",
+    "ethers": "^5.6.4",
     "file-saver": "^2.0.5",
     "formik": "2.2.9",
     "formik-material-ui": "3.0.1",