### 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.
action="store_false",
    default=True,
)
ARG_UPSTREAM = Arg(("-u", "--upstream"), help="Include upstream tasks", action="store_true")
ARG_ONLY_FAILED = Arg(("-f", "--only-failed"), help="Only failed jobs", action="store_true")
ARG_ONLY_RUNNING = Arg(("-r", "--only-running"), help="Only running jobs", action="store_true")
ARG_DOWNSTREAM = Arg(("-d", "--downstream"), help="Include downstream tasks", action="store_true")
ARG_EXCLUDE_SUBDAGS = Arg(("-x", "--exclude-subdags"), help="Exclude subdags", action="store_true")
ARG_EXCLUDE_PARENTDAG = Arg(
    ("-X", "--exclude-parentdag"),
    help="Exclude ParentDAGS if the task cleared is a part of a SubDAG",
    action="store_true",
)
ARG_DAG_REGEX = Arg(
    ("-R", "--dag-regex"), help="Search dag_id as regex instead of exact string", action="store_true"
)
ARG_SAVE = Arg(("-s", "--save"), help="Saves the result to the indicated file.")
ARG_IMGCAT = Arg(("--imgcat",), help="Displays graph using the imgcat tool.", action="store_true")
ARG_RUN_ID = Arg(("-r", "--run-id"), help="Helps to identify this run")
ARG_CONF = Arg(("-c", "--conf"), help="JSON string that gets pickled into the DagRun's conf attribute")
ARG_EXEC_DATE = Arg(("-e", "--exec-date"), help="The execution date of the DAG", type=parsedate)
ARG_REPLACE_MICRO = Arg(
    ("--no-replace-microseconds",),
    help="whether microseconds should be zeroed",
    dest="replace_microseconds",
    action="store_false",
    default=True,
)
ARG_DB_TABLES = Arg(
    ("-t", "--tables"),