### 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)

default=conf.get("webserver", "WEB_SERVER_WORKER_TIMEOUT"),
    type=int,
    help="The timeout for waiting on webserver workers",
)
ARG_HOSTNAME = Arg(
    ("-H", "--hostname"),
    default=conf.get("webserver", "WEB_SERVER_HOST"),
    help="Set the hostname on which to run the web server",
)
ARG_DEBUG = Arg(
    ("-d", "--debug"), help="Use the server that ships with Flask in debug mode", action="store_true"
)
ARG_ACCESS_LOGFILE = Arg(
    ("-A", "--access-logfile"),
    default=conf.get("webserver", "ACCESS_LOGFILE"),
    help="The logfile to store the webserver access log. Use '-' to print to stdout",
)
ARG_ERROR_LOGFILE = Arg(
    ("-E", "--error-logfile"),
    default=conf.get("webserver", "ERROR_LOGFILE"),
    help="The logfile to store the webserver error log. Use '-' to print to stderr",
)
ARG_ACCESS_LOGFORMAT = Arg(
    ("-L", "--access-logformat"),
    default=conf.get("webserver", "ACCESS_LOGFORMAT"),
    help="The access log format for gunicorn logs",
)
ARG_INTERNAL_API_PORT = Arg(
    ("-p", "--port"),
    default=9080,