fix spellin mistake

Author: Joe Burgess

index.ipynb

@@ -145,7 +145,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "> We assign the varible `italy` equal to `None`, but you should change the word `None` to code that uses the `countries` list to assign `italy` to `'Italy'`.  We wrote the variable `italy` a second time, so that you can see what it equals when you run the code block.  Currently, nothing is displayed below as it equals `None`, but when it's correct it will match the string which is commented out, `'Italy'`."
+    "> We assign the variable `italy` equal to `None`, but you should change the word `None` to code that uses the `countries` list to assign `italy` to `'Italy'`.  We wrote the variable `italy` a second time, so that you can see what it equals when you run the code block.  Currently, nothing is displayed below as it equals `None`, but when it's correct it will match the string which is commented out, `'Italy'`."
    ]
   },
   {