minor #7308 [Fix][httpKernel] Wrong links (20uf)

This PR was submitted for the 3.2 branch but it was merged into the 3.1 branch instead (closes #7308).

Discussion
----------

[Fix][httpKernel] Wrong links

Hello here,

### Problem
Fixes bad links pointing to the HttpKernel api.
http://symfony.com/doc/current/components/http_kernel.html#the-kernel-request-event

Happy New Year !

Commits
-------

3992434 [Fix][httpKernel] Wrong links

Author: xabbuh

components/http_kernel.rst

@@ -124,9 +124,9 @@ For general information on adding listeners to the events below, see
 
 .. caution::
 
-    As of 3.1 the :class:`Symfony\\Component\\Httpkernel\\HttpKernel` accepts a
+    As of 3.1 the :class:`Symfony\\Component\\HttpKernel\\HttpKernel` accepts a
     fourth argument, which must be an instance of
-    :class:`Symfony\\Component\\Httpkernel\\Controller\\ArgumentResolverInterface`.
+    :class:`Symfony\\Component\\HttpKernel\\Controller\\ArgumentResolverInterface`.
     In 4.0 this argument will become mandatory.
 
 .. seealso::