fix: remove incorrect 'is_stop' parameter from lens surface additions

Author: HarrisonKramer

docs/gallery/reflective/three_mirror_anastigmat.ipynb

@@ -57,14 +57,14 @@
     "               [ 4.87006021e-05, -1.70308923e-05,  2.12362562e-05,  1.51092539e-05],\n",
     "               [-1.04657810e-05, -2.25376153e-05, -8.02314506e-06,  3.02373985e-06]])\n",
     "lens.add_surface(index=2, radius=-100.019, thickness=20.0003, conic=-2.21455e-07, material='mirror',\n",
-    "                 rx=-0.174532, dy=-11.5, is_stop=True, surface_type='polynomial', coefficients=c2)\n",
+    "                 rx=-0.174532, dy=-11.5, surface_type='polynomial', coefficients=c2)\n",
     "\n",
     "c3 = np.array([[ 2.05787912e-05, -2.05604065e-05,  2.54616632e-05, -3.62841214e-05],\n",
     "               [ 6.24577550e-10,  1.09936457e-07, -2.69199040e-06, -1.05068667e-05],\n",
     "               [-3.28005504e-05,  1.88336844e-05, -3.34058539e-05,  4.93261709e-06],\n",
     "               [ 6.09659324e-07, -1.58589636e-06, -1.16163570e-05, -2.26243673e-05]])\n",
     "lens.add_surface(index=3, radius=-99.9774, thickness=-20.0003, conic=5.32063e-08, material='mirror',\n",
-    "                 rx=-0.0174547, dy=-15, is_stop=True, surface_type='polynomial', coefficients=c3)\n",
+    "                 rx=-0.0174547, dy=-15, surface_type='polynomial', coefficients=c3)\n",
     "\n",
     "lens.add_surface(index=4, dy=-19.3)"
    ]