fix: Rename argument mata-var in download help CLI

[jjjermiah]

          Looks great! And super easy to use. 

I think the only thing that could be improved is actually in the orcestra-datasets level, so I'll leave an issue there about it. But the help for the download function looks like

% readii-datasets radiomicsets download -h
Usage: readii-datasets radiomicsets download [OPTIONS] [NAME OF DATASET]

  Download a file for this dataset.

and then the table has these headings:

% readii-datasets radiomicsets table
                                      Radiomicsets                                       
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━┳━━━━━━━━━━━┓
┃ Name                             ┃ Dataset Name            ┃ Date Created ┃ Datatypes ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━╇━━━━━━━━━━━┩
│ HNSCC_Features                   │ HNSCC                   │ 2024-11-20   │ radiomics │
│ RADCURE_Features                 │ RADCURE                 │ 2024-11-20   │ radiomics │
│ HEAD-NECK-RADIOMICS-HN1_Features │ HEAD-NECK-RADIOMICS-HN1 │ 2024-11-20   │ radiomics │
└──────────────────────────────────┴─────────────────────────┴──────────────┴───────────┘

so it's not immediately clear what [NAME OF DATASET] is referring to.

Originally posted by @strixy16 in #80 (review)

[jjjermiah]

all thats needed is to pin orcestra-downloader minimum version to 0.11 with the new fix