Remove unused dependency.

Author: ghengeveld

package.json

@@ -48,7 +48,6 @@
     "babel-cli": "6.26.0",
     "babel-eslint": "10.0.1",
     "babel-preset-env": "1.7.0",
-    "babel-preset-flow": "6.23.0",
     "babel-preset-react": "6.24.1",
     "eslint": "5.11.1",
     "eslint-config-prettier": "3.3.0",