### Description

Currently, the `airflow variables export` command requires an explicit file path and does not support output to stdout. However connections can be printed to stdout using `airflow connections export -`. This inconsistency between the two export commands can lead to confusion and limits the flexibility of the variables export command.

### Use case/motivation

To bring some consistency, similar to connections, variables should also be printed to STDOUT, using `-` instead of filename. 

### Related issues

_No response_

### Are you willing to submit a PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

ActionCommand(
        name="delete",
        help="Delete role",
        func=lazy_load_command("airflow.cli.commands.role_command.roles_delete"),
        args=(ARG_ROLES, ARG_VERBOSE),
    ),
    ActionCommand(
        name="add-perms",
        help="Add roles permissions",
        func=lazy_load_command("airflow.cli.commands.role_command.roles_add_perms"),
        args=(ARG_ROLES, ARG_ROLE_RESOURCE, ARG_ROLE_ACTION_REQUIRED, ARG_VERBOSE),
    ),
    ActionCommand(
        name="del-perms",
        help="Delete roles permissions",
        func=lazy_load_command("airflow.cli.commands.role_command.roles_del_perms"),
        args=(ARG_ROLES, ARG_ROLE_RESOURCE, ARG_ROLE_ACTION, ARG_VERBOSE),
    ),
    ActionCommand(
        name="export",
        help="Export roles (without permissions) from db to JSON file",
        func=lazy_load_command("airflow.cli.commands.role_command.roles_export"),
        args=(ARG_ROLE_EXPORT, ARG_ROLE_EXPORT_FMT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="import",
        help="Import roles (without permissions) from JSON file to db",
        func=lazy_load_command("airflow.cli.commands.role_command.roles_import"),
        args=(ARG_ROLE_IMPORT, ARG_VERBOSE),
    ),