fix: upgrade @material-ui/core from 4.12.2 to 4.12.3

Snyk has created this PR to upgrade @material-ui/core from 4.12.2 to 4.12.3.

See this package in npm:
https://www.npmjs.com/package/@material-ui/core

See this project in Snyk:
https://app.snyk.io/org/olavoparno/project/ced911b6-827f-44a2-b45d-56d8e9af7970?utm_source=github&utm_medium=upgrade-pr

Author: snyk-bot

example/package-lock.json

@@ -5,7 +5,7 @@
   "license": "MIT",
   "private": true,
   "dependencies": {
-    "@material-ui/core": "^4.12.2",
+    "@material-ui/core": "^4.12.3",
     "react": "file:../node_modules/react",
     "react-dom": "^17.0.2",
     "react-scripts": "file:../node_modules/react-scripts",