### 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)

help="Remove role from a user",
        func=lazy_load_command("airflow.cli.commands.user_command.remove_role"),
        args=(ARG_USERNAME_OPTIONAL, ARG_EMAIL_OPTIONAL, ARG_ROLE, ARG_VERBOSE),
    ),
    ActionCommand(
        name="import",
        help="Import users",
        func=lazy_load_command("airflow.cli.commands.user_command.users_import"),
        args=(ARG_USER_IMPORT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="export",
        help="Export all users",
        func=lazy_load_command("airflow.cli.commands.user_command.users_export"),
        args=(ARG_USER_EXPORT, ARG_VERBOSE),
    ),
)
ROLES_COMMANDS = (
    ActionCommand(
        name="list",
        help="List roles",
        func=lazy_load_command("airflow.cli.commands.role_command.roles_list"),
        args=(ARG_PERMISSIONS, ARG_OUTPUT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="create",
        help="Create role",
        func=lazy_load_command("airflow.cli.commands.role_command.roles_create"),
        args=(ARG_ROLES, ARG_VERBOSE),
    ),