[Components][Filesystem] Move version hint for dumpFile method

Author: bicpi

components/filesystem.rst

@@ -229,12 +229,12 @@ isAbsolutePath
     // return false
     $fs->isAbsolutePath('../dir');
 
-.. versionadded:: 2.3
-    ``dumpFile`` is new in Symfony 2.3
-
 dumpFile
 ~~~~~~~~
 
+.. versionadded:: 2.3
+``dumpFile`` is new in Symfony 2.3
+
 :method:`Symfony\\Component\\Filesystem\\Filesystem::dumpFile` allows you to
 dump contents to a file. It does this in an atomic manner: it writes a temporary
 file first and then moves it to the new file location when it's finished.