### 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)

"\n"
            "The file format is determined by the file extension. "
            "For more information about supported "
            "format, see: https://www.graphviz.org/doc/info/output.html\n"
            "\n"
            "If you want to create a PNG file then you should execute the following command:\n"
            "airflow dags show-dependencies --save output.png\n"
            "\n"
            "If you want to create a DOT file then you should execute the following command:\n"
            "airflow dags show-dependencies --save output.dot\n"
        ),
        func=lazy_load_command("airflow.cli.commands.dag_command.dag_dependencies_show"),
        args=(
            ARG_SUBDIR,
            ARG_SAVE,
            ARG_IMGCAT,
            ARG_VERBOSE,
        ),
    ),
    ActionCommand(
        name="backfill",
        help="Run subsections of a DAG for a specified date range",
        description=(
            "Run subsections of a DAG for a specified date range. If reset_dag_run option is used, "
            "backfill will first prompt users whether airflow should clear all the previous dag_run and "
            "task_instances within the backfill date range. If rerun_failed_tasks is used, backfill "
            "will auto re-run the previous failed task instances  within the backfill date range"
        ),
        func=lazy_load_command("airflow.cli.commands.dag_command.dag_backfill"),
        args=(