chore(package): update eslint-plugin-flowtype to version 4.2.0

Closes #886

Author: greenkeeper[bot]

package.json

@@ -54,7 +54,7 @@
     "core-js": "3.2.0",
     "cross-env": "5.2.0",
     "eslint": "6.1.0",
-    "eslint-plugin-flowtype": "3.13.0",
+    "eslint-plugin-flowtype": "4.2.0",
     "express": "4.17.1",
     "gulp": "4.0.2",
     "gulp-babel": "8.0.0",