### 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="list",
        help="List connections",
        func=lazy_load_command("airflow.cli.commands.connection_command.connections_list"),
        args=(ARG_OUTPUT, ARG_VERBOSE, ARG_CONN_ID_FILTER),
    ),
    ActionCommand(
        name="add",
        help="Add a connection",
        func=lazy_load_command("airflow.cli.commands.connection_command.connections_add"),
        args=(ARG_CONN_ID, ARG_CONN_URI, ARG_CONN_JSON, ARG_CONN_EXTRA) + tuple(ALTERNATIVE_CONN_SPECS_ARGS),
    ),
    ActionCommand(
        name="delete",
        help="Delete a connection",
        func=lazy_load_command("airflow.cli.commands.connection_command.connections_delete"),
        args=(ARG_CONN_ID, ARG_COLOR, ARG_VERBOSE),
    ),
    ActionCommand(
        name="export",
        help="Export all connections",
        description=(
            "All connections can be exported in STDOUT using the following command:\n"
            "airflow connections export -\n"
            "The file format can be determined by the provided file extension. E.g., The following "
            "command will export the connections in JSON format:\n"
            "airflow connections export /tmp/connections.json\n"
            "The --file-format parameter can be used to control the file format. E.g., "
            "the default format is JSON in STDOUT mode, which can be overridden using: \n"