### Body

The CLI:

`airflow variables set [-h] [-j] [-v] key VALUE`

https://airflow.apache.org/docs/apache-airflow/stable/cli-and-env-variables-ref.html#set_repeat1

Doesn't support adding description though column exists and we support it from Rest API:
https://airflow.apache.org/docs/apache-airflow/stable/stable-rest-api-ref.html#operation/post_variables

**The Task:**

Allow to set description from cli command

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
help="Get a connection",
        func=lazy_load_command("airflow.cli.commands.connection_command.connections_get"),
        args=(ARG_CONN_ID, ARG_COLOR, ARG_OUTPUT, ARG_VERBOSE),
    ),
    ActionCommand(
        name="list",
        help="List connections",
        func=lazy_load_command("airflow.cli.commands.connection_command.connections_list"),
        args=(ARG_OUTPUT, ARG_VERBOSE, ARG_CONN_ID_FILTER),
    ),
    ActionCommand(
        name="add",
        help="Add a connection",
        func=lazy_load_command("airflow.cli.commands.connection_command.connections_add"),
        args=(ARG_CONN_ID, ARG_CONN_URI, ARG_CONN_JSON, ARG_CONN_EXTRA, *ALTERNATIVE_CONN_SPECS_ARGS),
    ),
    ActionCommand(
        name="delete",
        help="Delete a connection",
        func=lazy_load_command("airflow.cli.commands.connection_command.connections_delete"),
        args=(ARG_CONN_ID, ARG_COLOR, ARG_VERBOSE),
    ),
    ActionCommand(
        name="export",
        help="Export all connections",
        description=(
            "All connections can be exported in STDOUT using the following command:\n"
            "airflow connections export -\n"
            "The file format can be determined by the provided file extension. E.g., The following "
            "command will export the connections in JSON format:\n"