minor #6720 [Component][ClassLoader]Remove invalid note (rendler-denis)

This PR was submitted for the 3.0 branch but it was merged into the 2.7 branch instead (closes #6720).

Discussion
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[Component][ClassLoader]Remove invalid note

- remove the note mentioning that a class loader from this component is registered in app/autoload.php because in fact it loads Composer's autoloader

Commits
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314e64c [Component][ClassLoader]Remove invalid note

components/class_loader/class_loader.rst

@@ -33,11 +33,6 @@ is straightforward::
 
     $loader->register();
 
-.. note::
-
-    The autoloader is automatically registered in a Symfony application
-    (see ``app/autoload.php``).
-
 Use :method:`Symfony\\Component\\ClassLoader\\ClassLoader::addPrefix` or
 :method:`Symfony\\Component\\ClassLoader\\ClassLoader::addPrefixes` to register
 your classes::