chore(java-sdk): Update Maven group ID to 'dev.openfga'

[booniepepper]

Description

The Auth0 folks prefer the shorter 'dev.openfga' group id

References

Generates https://github.com/openfga/java-sdk/pull/18

Review Checklist

• [ ] I have clicked on "allow edits by maintainers".
• [ ] I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• [ ] The correct base branch is being used, if not main
• [ ] I have added tests to validate that the change in functionality is working as expected