[Multi-bucket] fix - disable firefox browser test for nextjs auth

[jjarvisp]

Description of changes

The purpose of this pull request is to disable the firefox Next.js storage integration test. There exists several issues between Firefox and Cypress that cause issues when testing using secure cookies (which are required in the Next.js context). These issues can be mitigated locally but not in CI without additional effort.

Failing on Firefox and succeeding on Chrome in CI.
https://github.com/jjarvisp/amplify-js/actions/runs/10113370892

Cypress / Firefox issues:
cypress-io/cypress#18690
cypress-io/cypress#18217

Issue #, if available

Description of how you validated changes

https://github.com/jjarvisp/amplify-js/actions/runs/10148754990

Checklist

• PR description included
• yarn test passes
• Unit Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

Checklist for repo maintainers

• Verify E2E tests for existing workflows are working as expected or add E2E tests for newly added workflows
• New source file paths included in this PR have been added to CODEOWNERS, if appropriate

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.