Upgrade Angular to the latest version in the Spring Boot Angular example.

Author: bsautel

examples/spring-boot-angular/webapp/angular.json

@@ -43,7 +43,6 @@
               "optimization": true,
               "outputHashing": "all",
               "sourceMap": false,
-              "extractCss": true,
               "namedChunks": false,
               "extractLicenses": true,
               "vendorChunk": false,