chore: update 'chart' demo for nativescript-ui-chart v7.1.1

Author: nsplugins

chart/package.json

@@ -50,7 +50,7 @@
     "nativescript-css-loader": "~0.26.0",
     "nativescript-dev-appium": "^6.0.0",
     "nativescript-dev-webpack": "^1.3.0",
-    "tns-platform-declarations": "^6.2.0",
+    "tns-platform-declarations": "^6.3.1",
     "tslint": "~5.11.0",
     "typescript": "~3.5.3"
   }