### 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=lazy_object_proxy.Proxy(
        lambda: f"Table names to perform maintenance on (use comma-separated list).\n"
        f"Options: {import_string('airflow.cli.commands.db_command.all_tables')}"
    ),
    type=string_list_type,
)
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",
)