typos fixed

Author: petk

book/testing.rst

@@ -245,7 +245,7 @@ document::
 
     The ``server`` array is the raw values that you'd expect to normally
     find in the PHP `$_SERVER`_ superglobal. For example, to set the `Content-Type`,
-    `Referer` and `X-Requested-With' HTTP headers, you'd pass the following (mind
+    `Referer` and `X-Requested-With` HTTP headers, you'd pass the following (mind
     the `HTTP_` prefix for non standard headers)::
 
         $client->request(

reference/constraints/Choice.rst

@@ -124,7 +124,7 @@ form element.
         }
     }
 
-You can pass the name of this method to the `callback_` option of the ``Choice``
+You can pass the name of this method to the `callback`_ option of the ``Choice``
 constraint.
 
 .. configuration-block::