Bump xml2js and @microsoft/sp-build-web

Bumps [xml2js](https://github.com/Leonidas-from-XIV/node-xml2js) to 0.5.0 and updates ancestor dependency [@microsoft/sp-build-web](http://aka.ms/spfx). These dependencies need to be updated together.


Updates `xml2js` from 0.4.23 to 0.5.0
- [Commits](https://github.com/Leonidas-from-XIV/node-xml2js/commits/0.5.0)

Updates `@microsoft/sp-build-web` from 1.15.2 to 1.17.2

---
updated-dependencies:
- dependency-name: xml2js
  dependency-type: indirect
- dependency-name: "@microsoft/sp-build-web"
  dependency-type: direct:development
...

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

samples/angularelements-helloworld/package.json

@@ -34,7 +34,7 @@
     "zone.js": "^0.8.26"
   },
   "devDependencies": {
-    "@microsoft/sp-build-web": "~1.15.2",
+    "@microsoft/sp-build-web": "~1.17.2",
     "@microsoft/sp-module-interfaces": "~1.4.1",
     "@microsoft/sp-webpart-workbench": "~1.12.1",
     "@types/chai": ">=3.4.34 <3.6.0",