Bump flatted in /sample/applicationinsights-angularplugin-sample

Bumps [flatted](https://github.com/WebReflection/flatted) from 3.3.1 to 3.4.2.
- [Commits](WebReflection/flatted@v3.3.1...v3.4.2)

---
updated-dependencies:
- dependency-name: flatted
  dependency-version: 3.4.2
  dependency-type: indirect
...

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

Author: dependabot[bot]