Timeouts: Stnadardise pageLoad rather than page load

A previous change (#787) changed `page load` to `pageLoad`
but we missed the similar change in the `timeouts configuration
object`.

Author: shs96c

webdriver-spec.html

@@ -2066,7 +2066,7 @@ <h3>Timeouts</h3>
  </tr>
 
  <tr>
-  <td>"<code>page load</code>"
+  <td>"<code>pageLoad</code>"
   <td>number
   <td>Specifies the <a>session page load timeout</a>.
  </tr>