### 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)

ARG_DO_PICKLE,
            ARG_PID,
            ARG_DAEMON,
            ARG_STDOUT,
            ARG_STDERR,
            ARG_LOG_FILE,
            ARG_SKIP_SERVE_LOGS,
            ARG_VERBOSE,
        ),
        epilog=(
            "Signals:\n"
            "\n"
            "  - SIGUSR2: Dump a snapshot of task state being tracked by the executor.\n"
            "\n"
            "    Example:\n"
            '        pkill -f -USR2 "airflow scheduler"'
        ),
    ),
    ActionCommand(
        name="triggerer",
        help="Start a triggerer instance",
        func=lazy_load_command("airflow.cli.commands.triggerer_command.triggerer"),
        args=(
            ARG_PID,
            ARG_DAEMON,
            ARG_STDOUT,
            ARG_STDERR,
            ARG_LOG_FILE,
            ARG_CAPACITY,
            ARG_VERBOSE,