Bump yaml and stylelint in /samples/react-enhanced-powerapps

Removes [yaml](https://github.com/eemeli/yaml). It's no longer used after updating ancestor dependency [stylelint](https://github.com/stylelint/stylelint). These dependencies need to be updated together.


Removes `yaml`

Updates `stylelint` from 13.6.1 to 15.6.0
- [Release notes](https://github.com/stylelint/stylelint/releases)
- [Changelog](https://github.com/stylelint/stylelint/blob/main/CHANGELOG.md)
- [Commits](https://github.com/stylelint/stylelint/compare/13.6.1...15.6.0)

---
updated-dependencies:
- dependency-name: yaml
  dependency-type: indirect
- dependency-name: stylelint
  dependency-type: direct:development
...

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

samples/react-enhanced-powerapps/package.json

@@ -43,7 +43,7 @@
         "gulp": "~4.0.2",
         "gulp-sequence": "1.0.0",
         "gulp-stylelint": "^13.0.0",
-        "stylelint": "^13.6.1",
+        "stylelint": "^15.6.0",
         "stylelint-config-css-modules": "^2.2.0",
         "stylelint-config-standard": "^20.0.0",
         "stylelint-scss": "^3.18.0",