Bump validator and @sap/approuter in /app

Bumps [validator](https://github.com/validatorjs/validator.js) to 13.15.23 and updates ancestor dependency @sap/approuter. These dependencies need to be updated together.


Updates `validator` from 13.15.20 to 13.15.23
- [Release notes](https://github.com/validatorjs/validator.js/releases)
- [Changelog](https://github.com/validatorjs/validator.js/blob/master/CHANGELOG.md)
- [Commits](validatorjs/validator.js@13.15.20...13.15.23)

Updates `@sap/approuter` from 20.8.3 to 20.8.4

---
updated-dependencies:
- dependency-name: validator
  dependency-version: 13.15.23
  dependency-type: indirect
- dependency-name: "@sap/approuter"
  dependency-version: 20.8.4
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]