### 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)

type=int,
    help="The port on which to run the server",
)
ARG_INTERNAL_API_WORKERS = Arg(
    ("-w", "--workers"),
    default=4,
    type=int,
    help="Number of workers to run the Internal API-on",
)
ARG_INTERNAL_API_WORKERCLASS = Arg(
    ("-k", "--workerclass"),
    default="sync",
    choices=["sync", "eventlet", "gevent", "tornado"],
    help="The worker class to use for Gunicorn",
)
ARG_INTERNAL_API_WORKER_TIMEOUT = Arg(
    ("-t", "--worker-timeout"),
    default=120,
    type=int,
    help="The timeout for waiting on Internal API workers",
)
ARG_INTERNAL_API_HOSTNAME = Arg(
    ("-H", "--hostname"),
    default="0.0.0.0",
    help="Set the hostname on which to run the web server",
)
ARG_INTERNAL_API_ACCESS_LOGFILE = Arg(
    ("-A", "--access-logfile"),
    help="The logfile to store the access log. Use '-' to print to stdout",
)