### 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)

)
VARIABLES_COMMANDS = (
    ActionCommand(
        name="list",
        help="List variables",
        func=lazy_load_command("airflow.cli.commands.variable_command.variables_list"),
        args=(ARG_OUTPUT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="get",
        help="Get variable",
        func=lazy_load_command("airflow.cli.commands.variable_command.variables_get"),
        args=(ARG_VAR, ARG_DESERIALIZE_JSON, ARG_DEFAULT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="set",
        help="Set variable",
        func=lazy_load_command("airflow.cli.commands.variable_command.variables_set"),
        args=(ARG_VAR, ARG_VAR_VALUE, ARG_SERIALIZE_JSON, ARG_VERBOSE),
    ),
    ActionCommand(
        name="delete",
        help="Delete variable",
        func=lazy_load_command("airflow.cli.commands.variable_command.variables_delete"),
        args=(ARG_VAR, ARG_VERBOSE),
    ),
    ActionCommand(
        name="import",
        help="Import variables",
        func=lazy_load_command("airflow.cli.commands.variable_command.variables_import"),