Update basic.html

Fix secret word to not be capitalised to match expectations in Udacity checker.

lesson1-overview/06-experiencing-screen-reader/basic.html

@@ -25,7 +25,7 @@ <h1>Click the button!</h1>
         <h1>We love accessibility too!</h1>
         <img src="koala.jpg" alt="Koala" tabindex="-1" id="koala">
         <p>
-          The secret word is "Koala".
+          The secret word is "koala".
         </p>
         <button id="close">Close dialog</button>
       </div>