Bump vlucas/phpdotenv from 5.6.3 to 5.6.4 in /user-auth/graphtutorial

Bumps [vlucas/phpdotenv](https://github.com/vlucas/phpdotenv) from 5.6.3 to 5.6.4.
- [Release notes](https://github.com/vlucas/phpdotenv/releases)
- [Commits](vlucas/phpdotenv@v5.6.3...v5.6.4)

---
updated-dependencies:
- dependency-name: vlucas/phpdotenv
  dependency-version: 5.6.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]