Bump ajv from 6.10.0 to 6.12.3 in /client

Bumps [ajv](https://github.com/ajv-validator/ajv) from 6.10.0 to 6.12.3.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v6.10.0...v6.12.3)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

client/package.json

@@ -7,7 +7,7 @@
 		"@material-ui/icons": "^4.9.1",
 		"@truffle/hdwallet-provider": "^1.0.18",
 		"acorn": "^6.0.7",
-		"ajv": "^6.8.1",
+		"ajv": "^6.12.3",
 		"bignumber.js": "^8.0.1",
 		"connected-react-router": "^6.3.2",
 		"fork-ts-checker-webpack-plugin": "^0.2.10",