Fixing minor typo in comment

Changing getRoutes to getJsons to reflect function name in use. Makes it the same as the function name in the comment in the solution.

Author: emily-li

ch12.md

@@ -267,7 +267,7 @@ Map Route Route → Task Error (Map Route JSON)
 
 {% initial src="./exercises/ch12/exercise_a.js#L11;" %}  
 ```js  
-// getRoutes :: Map Route Route -> Map Route (Task Error JSON)
+// getJsons :: Map Route Route -> Map Route (Task Error JSON)
 const getJsons = map(httpGet);
 ```