chore(deps): update dependency react-dom to v16.12.0 (#660)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

tests/integration/package.json

@@ -13,7 +13,7 @@
     "@zeit/next-css": "1.0.1",
     "next": "5.1.0",
     "react": "16.12.0",
-    "react-dom": "16.3.3"
+    "react-dom": "16.12.0"
   },
   "devDependencies": {
     "cypress": "2.1.0"