fix(meta): remove standalone as breaks galaxy_importer

[juju4]

Description

remove standalone as breaks galaxy_importer

Motivation and Context

Try fixing galaxy role release
https://github.com/juju4/ansible-adduser/actions/runs/11990259755

and
galaxy_importer.exceptions.LegacyRoleSchemaError: unknown field in galaxy_info: LegacyGalaxyInfo.__init__() got an unexpected keyword argument 'standalone'

How Has This Been Tested?

To be test after in main and ansible-galaxy role import --branch main juju4 ansible-adduser

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed including pre-commit and github actions.
• Used in production.

[juju4]

Manual import is successful
https://galaxy.ansible.com/ui/standalone/roles/juju4/adduser/versions/

Opened issue for non-working action robertdebock/galaxy-action#14