Remove react-dom peer dep from react-apollo/hooks

Fixes apollographql#3704 

Looked through all the files for this package and I didn't see any usage of `react-dom` so its unnecessary as a peer dep. I didn't check other packages, so its possible the peer dep is extraneous elsewhere as well.

Author: maclockard

packages/hooks/package.json

@@ -39,8 +39,7 @@
     "@types/react": "^16.8.0",
     "apollo-client": "^2.6.4",
     "graphql": "^14.3.1",
-    "react": "^16.8.0",
-    "react-dom": "^16.8.0"
+    "react": "^16.8.0"
   },
   "dependencies": {
     "@apollo/react-common": "file:../common",