STY: Fix notebook

Author: bashtage

examples/system_examples.ipynb

@@ -331,7 +331,7 @@
     "        res.params.iloc[1::7],\n",
     "        res.std_errors.iloc[1::7],\n",
     "    ],\n",
-    "    1,\n",
+    "    axis=1,\n",
     ")\n",
     "params.columns = [\"OLS\", \"OLS se\", \"GLS\", \"GLS se\"]\n",
     "params.index = regions\n",
@@ -780,7 +780,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.16"
+   "version": "3.10.10"
   },
   "pycharm": {
    "stem_cell": {