### 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_DB_CLEANUP_TIMESTAMP = Arg(
    ("--clean-before-timestamp",),
    help="The date or timestamp before which data should be purged.\n"
    "If no timezone info is supplied then dates are assumed to be in airflow default timezone.\n"
    "Example: '2022-01-01 00:00:00+01:00'",
    type=parsedate,
    required=True,
)
ARG_DB_DRY_RUN = Arg(
    ("--dry-run",),
    help="Perform a dry run",
    action="store_true",
)
ARG_DB_SKIP_ARCHIVE = Arg(
    ("--skip-archive",),
    help="Don't preserve purged records in an archive table.",
    action="store_true",
)
ARG_DB_EXPORT_FORMAT = Arg(
    ("--export-format",),
    help="The file format to export the cleaned data",
    choices=("csv",),
    default="csv",
)
ARG_DB_OUTPUT_PATH = Arg(
    ("--output-path",),
    metavar="DIRPATH",
    help="The path to the output directory to export the cleaned data. This directory must exist.",
    required=True,