### 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="logging",
        help="Get information about task logging handlers provided",
        func=lazy_load_command("airflow.cli.commands.provider_command.logging_list"),
        args=(ARG_OUTPUT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="secrets",
        help="Get information about secrets backends provided",
        func=lazy_load_command("airflow.cli.commands.provider_command.secrets_backends_list"),
        args=(ARG_OUTPUT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="auth",
        help="Get information about API auth backends provided",
        func=lazy_load_command("airflow.cli.commands.provider_command.auth_backend_list"),
        args=(ARG_OUTPUT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="executors",
        help="Get information about executors provided",
        func=lazy_load_command("airflow.cli.commands.provider_command.executors_list"),
        args=(ARG_OUTPUT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="notifications",
        help="Get information about notifications provided",
        func=lazy_load_command("airflow.cli.commands.provider_command.notifications_list"),
        args=(ARG_OUTPUT, ARG_VERBOSE),
    ),