chore(package): update apollo-client to version 2.6.6

Closes #6282

Author: greenkeeper[bot]

package.json

@@ -65,7 +65,7 @@
     "@babel/preset-env": "7.7.6",
     "@parse/minami": "1.0.0",
     "apollo-cache-inmemory": "1.6.5",
-    "apollo-client": "2.6.4",
+    "apollo-client": "2.6.6",
     "apollo-link": "1.2.13",
     "apollo-link-http": "1.5.16",
     "apollo-link-ws": "1.0.19",