Update dependency prop-types to v15.8.1

Author: renovate[bot]

package-lock.json

@@ -32,7 +32,7 @@
     "pre-commit": "1.2.2",
     "prettier": "1.19.1",
     "pretty-quick": "1.11.1",
-    "prop-types": "15.7.2",
+    "prop-types": "15.8.1",
     "react": "16.13.1",
     "react-dom": "16.13.1",
     "riteway": "6.1.2",