Bump phpunit/phpunit from 9.6.16 to 9.6.33 in /php/example_code/rds

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 9.6.16 to 9.6.33.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/9.6.33/ChangeLog-9.6.md)
- [Commits](sebastianbergmann/phpunit@9.6.16...9.6.33)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-version: 9.6.33
  dependency-type: direct:production
...

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

Author: dependabot[bot]