Revert "Bump eslint-plugin-flowtype from 5.10.0 to 7.0.0"

This reverts commit 86666c2.

Author: raymond-lam

package-lock.json

@@ -60,7 +60,7 @@
     "eslint-config-react-app": "^6.0.0",
     "eslint-config-standard": "^16.0.2",
     "eslint-config-standard-react": "^11.0.1",
-    "eslint-plugin-flowtype": "^7.0.0",
+    "eslint-plugin-flowtype": "^5.10.0",
     "eslint-plugin-import": "^2.22.1",
     "eslint-plugin-jsx-a11y": "^6.4.1",
     "eslint-plugin-node": "^11.0.0",