Fixed the Symfony version number

Author: javiereguiluz

cookbook/profiler/storage.rst

@@ -4,8 +4,8 @@
 Switching the Profiler Storage
 ==============================
 
-In Symfony versions previous to 2.8, profiles could be stored in files, databases,
-services like Redis and Memcache, etc. Starting from Symfony 2.8, the only storage
+In Symfony versions previous to 3.0, profiles could be stored in files, databases,
+services like Redis and Memcache, etc. Starting from Symfony 3.0, the only storage
 mechanism with built-in support is the filesystem.
 
 By default the profile stores the collected data in the ``%kernel.cache_dir%/profiler/``