Corrected typos in heat budget tutorial

Author: andrewdelman

Tutorials_as_Jupyter_Notebooks/ECCO_v4_Heat_budget_closure.ipynb

@@ -383,8 +383,8 @@
    "source": [
     "## Open ECCO monthly mean variables\n",
     "\n",
-    "ecco_vars_int = ds_dict[ShortNames[1]]\n",
-    "ecco_vars_sfc = ds_dict[ShortNames[2]]\n",
+    "ecco_vars_int = ds_dict[ShortNames_list[1]]\n",
+    "ecco_vars_sfc = ds_dict[ShortNames_list[2]]\n",
     "\n",
     "ecco_monthly_mean = xr.merge((ecco_vars_int,\\\n",
     "                              ecco_vars_sfc[['TFLUX','oceQsw']]))\n",