Update typo in ghci error (learnyouahaskell#44)

Author: phuc1nguyen

docs/starting-out.html

@@ -102,7 +102,7 @@ <h1 style="margin-left:-3px">Starting Out</h1>
 What about doing <span class="fixed">5 + "llama"</span> or <span class="fixed">5 == True</span>? Well, if we try the first snippet, we get a big scary error message!
 </p>
 <pre name="code" class="haskell: ghci">
-    • No instance for (Num [Char]) arising from a use of ‘+’
+    • No instance for (Num String) arising from a use of ‘+’
     • In the expression: 5 + "llama"
       In an equation for ‘it’: it = 5 + "llama"
 </pre>