Merge pull request #3161 from bicpi/fix_heading_levels

[Components][HttpKernel] Fix heading levels + typo

Author: weaverryan

components/http_kernel/introduction.rst

@@ -262,7 +262,7 @@ will be called after another event - ``kernel.controller`` - is dispatched.
 .. _component-http-kernel-kernel-controller:
 
 3) The ``kernel.controller`` event
-----------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 **Typical Purposes**: Initialize things or change the controller just before
 the controller is executed.
@@ -300,7 +300,7 @@ on the event object that's passed to listeners on this event.
     next section to see why this is important.
 
 4) Getting the Controller Arguments
------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Next, ``HttpKernel::handle`` calls
 :method:`Symfony\\Component\\HttpKernel\\Controller\\ControllerResolverInterface::getArguments`.
@@ -489,8 +489,8 @@ as possible to the client (e.g. sending emails).
 
 .. _component-http-kernel-kernel-exception:
 
-Handling Exceptions:: the ``kernel.exception`` event
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Handling Exceptions: the ``kernel.exception`` event
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 **Typical Purposes**: Handle some type of exception and create an appropriate
 ``Response`` to return for the exception