[book][bundles] Fixing markup problem

Author: weaverryan

book/bundles.rst

@@ -57,7 +57,7 @@ class name.
 
  Symfony2 core Bundles do not prefix the Bundle class with ``Symfony``
  and always add a ``Bundle`` subnamespace; for example:
- :class:``Symfony\Bundle\FrameworkBundle\FrameworkBundle``.
+ :class:`Symfony\\Bundle\\FrameworkBundle\\FrameworkBundle`.
 
 Directory Structure
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