fix(deps): update dependency @material-ui/core to v4.12.3

Author: renovate-bot

templates/fullstack/client/package.json

@@ -13,7 +13,7 @@
   "dependencies": {
     "@apollo/react-common": "3.1.4",
     "@apollo/react-hooks": "3.1.5",
-    "@material-ui/core": "4.11.3",
+    "@material-ui/core": "4.12.3",
     "apollo-boost": "0.4.9",
     "graphql": "15.5.1",
     "react": "17.0.2",