Update dependency prop-types to v15.7.1 (#704)

Author: renovate[bot]

src/React.Core/package-lock.json

@@ -15,7 +15,7 @@
     "gulp-uglify": "1.5.4",
     "json-loader": "0.5.7",
     "natives": "^1.1.6",
-    "prop-types": "15.6.0",
+    "prop-types": "15.7.1",
     "react": "16.7.0",
     "react-dom": "16.7.0",
     "vinyl-named": "1.1.0",