### 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)

name="set",
        help="Configure pool",
        func=lazy_load_command("airflow.cli.commands.pool_command.pool_set"),
        args=(
            ARG_POOL_NAME,
            ARG_POOL_SLOTS,
            ARG_POOL_DESCRIPTION,
            ARG_POOL_INCLUDE_DEFERRED,
            ARG_OUTPUT,
            ARG_VERBOSE,
        ),
    ),
    ActionCommand(
        name="delete",
        help="Delete pool",
        func=lazy_load_command("airflow.cli.commands.pool_command.pool_delete"),
        args=(ARG_POOL_NAME, ARG_OUTPUT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="import",
        help="Import pools",
        func=lazy_load_command("airflow.cli.commands.pool_command.pool_import"),
        args=(ARG_POOL_IMPORT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="export",
        help="Export all pools",
        func=lazy_load_command("airflow.cli.commands.pool_command.pool_export"),
        args=(ARG_POOL_EXPORT, ARG_VERBOSE),
    ),