Bump the npm_and_yarn at /samples/angularelements-helloworld security update group

Bumps the npm_and_yarn at /samples/angularelements-helloworld security update group in /samples/angularelements-helloworld with 2 updates: [@microsoft/generator-sharepoint](http://aka.ms/spfx) and [gulp](https://github.com/gulpjs/gulp).


Updates `@microsoft/generator-sharepoint` from 1.4.1 to 1.18.0

Updates `gulp` from 3.9.1 to 4.0.2
- [Release notes](https://github.com/gulpjs/gulp/releases)
- [Changelog](https://github.com/gulpjs/gulp/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gulpjs/gulp/compare/v3.9.1...v4.0.2)

---
updated-dependencies:
- dependency-name: "@microsoft/generator-sharepoint"
  dependency-type: direct:production
- dependency-name: gulp
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

samples/angularelements-helloworld/package.json

@@ -17,7 +17,7 @@
     "@angular/elements": "^6.0.3",
     "@angular/platform-browser": "^6.0.3",
     "@angular/platform-browser-dynamic": "^6.0.3",
-    "@microsoft/generator-sharepoint": "^1.4.1",
+    "@microsoft/generator-sharepoint": "^1.18.0",
     "@microsoft/sp-core-library": "~1.4.1",
     "@microsoft/sp-lodash-subset": "~1.4.1",
     "@microsoft/sp-office-ui-fabric-core": "~1.4.1",
@@ -40,7 +40,7 @@
     "@types/chai": ">=3.4.34 <3.6.0",
     "@types/mocha": ">=2.2.33 <2.6.0",
     "ajv": "~5.2.2",
-    "gulp": "~3.9.1",
+    "gulp": "~4.0.2",
     "uglifyjs-webpack-plugin": "^1.2.5",
     "webpack-bundle-analyzer": "^3.3.2"
   }