Update react-is requirement in /packages/material-ui-utils (#42)

Updates the requirements on [react-is](https://github.com/facebook/react/tree/HEAD/packages/react-is) to permit the latest version.
- [Release notes](https://github.com/facebook/react/releases)
- [Changelog](https://github.com/facebook/react/blob/master/CHANGELOG.md)
- [Commits](https://github.com/facebook/react/commits/v16.8.6/packages/react-is)

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

packages/material-ui-utils/package.json

@@ -39,7 +39,7 @@
   "dependencies": {
     "@babel/runtime": "^7.2.0",
     "prop-types": "^15.7.2",
-    "react-is": "^16.8.0"
+    "react-is": "^16.8.6"
   },
   "devDependencies": {},
   "sideEffects": false,