fix(package): update deepmerge to version 4.2.0

Closes #776

Author: greenkeeper[bot]

packages/admin-ui/package.json

@@ -24,7 +24,7 @@
     "@types/node": "^11.13.3",
     "@types/react": "^16.7.2",
     "@types/react-dom": "^16.0.9",
-    "deepmerge": "^3.0.0",
+    "deepmerge": "^4.2.0",
     "downshift": "^3.1.4",
     "emotion": "^10.0.0",
     "history": "^4.9.0",