### 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)

),
    GroupCommand(
        name="connections",
        help="Manage connections",
        subcommands=CONNECTIONS_COMMANDS,
    ),
    GroupCommand(
        name="providers",
        help="Display providers",
        subcommands=PROVIDERS_COMMANDS,
    ),
    GroupCommand(
        name="users",
        help="Manage users",
        subcommands=USERS_COMMANDS,
    ),
    GroupCommand(
        name="roles",
        help="Manage roles",
        subcommands=ROLES_COMMANDS,
    ),
    ActionCommand(
        name="sync-perm",
        help="Update permissions for existing roles and optionally DAGs",
        func=lazy_load_command("airflow.cli.commands.sync_perm_command.sync_perm"),
        args=(ARG_INCLUDE_DAGS, ARG_VERBOSE),
    ),
    ActionCommand(
        name="rotate-fernet-key",
        func=lazy_load_command("airflow.cli.commands.rotate_fernet_key_command.rotate_fernet_key"),