fixed typo

Author: fabpot

book/page_creation.rst

@@ -463,7 +463,7 @@ about each of these directories in later chapters.
  Because of the autoloader, you never need to worry about using ``include``
  or ``require`` statements. Instead, Symfony2 uses the namespace of a class
  to determine its location and automatically includes the file on your
- behalf the instance you need a class::
+ behalf the instant you need a class::
  
  $loader->registerNamespaces(array(
  'Acme' => __DIR__.'/../src',