fix: notebook url assembly

notebooks/01_tracks_prediction.ipynb

@@ -192,7 +192,7 @@
         "        return fa_path\n",
         "\n",
         "    # UCSC chrom fasta (chromFa/)\n",
-        "    url = f\"https://hgdownload.soe.ucsc.edu/goldenPath/${assembly}/chromosomes/{chrom}.fa.gz\"\n",
+        "    url = f\"https://hgdownload.soe.ucsc.edu/goldenPath/{assembly}/chromosomes/{chrom}.fa.gz\"\n",
         "    print(\"Downloading:\", url)\n",
         "    r = requests.get(url, stream=True)\n",
         "    r.raise_for_status()\n",