Bump wp-phpunit/wp-phpunit from 6.8.2 to 6.8.3

Bumps [wp-phpunit/wp-phpunit](https://github.com/wp-phpunit/wp-phpunit) from 6.8.2 to 6.8.3.
- [Commits](wp-phpunit/wp-phpunit@6.8.2...6.8.3)

---
updated-dependencies:
- dependency-name: wp-phpunit/wp-phpunit
  dependency-version: 6.8.3
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]