fix(java-sdk): Fix tests for assertions model changes

[jimmyjames]

Description

Fixes the java-sdk tests for writing assertions, which was caused by the API now allowing contextual tuples to be specified on the request to create assertions.

I created https://github.com/openfga/sdk-generator/issues/360 to update our models to support this in the SDK, but for now we're just fixing the tests.

(aside - we should look into if there's a way for the java SDK tests to not be so picky)

References

Unblocks https://github.com/openfga/sdk-generator/pull/359 and https://github.com/openfga/sdk-generator/pull/358

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

[jimmyjames]

Instead of this, a change was made to pin the OpenFGA API version: #362