Minor edit

Author: davewhipp

L1/a-taste-of-python.ipynb

@@ -639,7 +639,7 @@
     "editable": true
    },
    "source": [
-    "### Character input\n",
+    "### Character input (*optional*)\n",
     "\n",
     "Python and Jupyter notebooks also let us interact in another way with our code! The built-in [input()](https://docs.python.org/3.6/library/functions.html?highlight=input#input) function reads a line from input and returns it as a string.\n",
     "\n",