misprint fix

fix the `vector of x-coordinates` used in the example

Author: maxim-levy

tutorials/Introduction to Modeling in Gen.ipynb

@@ -202,7 +202,7 @@
    },
    "outputs": [],
    "source": [
-    "xs = [-5., -4., -3., -.2, -1., 0., 1., 2., 3., 4., 5.];"
+    "xs = [-5., -4., -3., -2., -1., 0., 1., 2., 3., 4., 5.];"
    ]
   },
   {