Update TCIA_PROSTATEx_Prostate_MRI_Anatomy_Model.ipynb (#1261)

Fixes [#1260](#1260).

### Description
Tcia-utils function downloadSeries() requires you to specify format =
"df" now if you want to return a dataframe.

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: kirbyju

model_zoo/TCIA_PROSTATEx_Prostate_MRI_Anatomy_Model.ipynb

@@ -224,7 +224,7 @@
     "cart_data = nbia.getSharedCart(cart_name)\n",
     "\n",
     "# download the series_uids list and return dataframe of metadata\n",
-    "df = nbia.downloadSeries(cart_data)\n",
+    "df = nbia.downloadSeries(cart_data, format=\"df\")\n",
     "\n",
     "# display dataframe\n",
     "# display(df)"