docs: update execution count in off-axis parabola notebook

Author: HarrisonKramer

docs/gallery/freeform/off_axis_parabola.ipynb

@@ -53,7 +53,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [
     {