Bump @material-ui/core from 4.11.4 to 4.12.3 in /client (#141)

Bumps [@material-ui/core](https://github.com/mui-org/material-ui/tree/HEAD/packages/material-ui) from 4.11.4 to 4.12.3.
- [Release notes](https://github.com/mui-org/material-ui/releases)
- [Changelog](https://github.com/mui-org/material-ui/blob/v4.12.3/CHANGELOG.md)
- [Commits](https://github.com/mui-org/material-ui/commits/v4.12.3/packages/material-ui)

---
updated-dependencies:
- dependency-name: "@material-ui/core"
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Connor Boyle <connor.bo@gmail.com>

client/package.json

@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "private": true,
   "dependencies": {
-    "@material-ui/core": "^4.11.4",
+    "@material-ui/core": "^4.12.3",
     "@material-ui/data-grid": "^4.0.0-alpha.30",
     "@material-ui/icons": "^4.11.2",
     "@testing-library/jest-dom": "^5.13.0",