chore(deps): update dependency @types/prop-types to v15.5.6

Author: renovate-bot

package-lock.json

@@ -40,7 +40,7 @@
     "@ht2-labs/typescript-project": "1.1.0",
     "@types/mocha": "5.2.5",
     "@types/power-assert": "1.5.0",
-    "@types/prop-types": "15.5.5",
+    "@types/prop-types": "15.5.6",
     "@types/react": "16.4.2",
     "@types/react-dom": "16.0.7",
     "assert-rejects": "0.1.1",