fix(demo): remove styleext property from angular.json

Author: shanmukhateja

demo/angular.json

@@ -181,8 +181,7 @@
  "defaultProject": "angular-datatables-demo",
  "schematics": {
  "@schematics/angular:component": {
- "prefix": "app",
- "styleext": "css"
+ "prefix": "app"
  },
  "@schematics/angular:directive": {
  "prefix": "app"