minor #6284 [Book] [Routing] Fix third param true to UrlGeneratorInterface::ABSOLUTE_URI (eriwin)

This PR was merged into the 2.3 branch.

Discussion
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[Book] [Routing] Fix third param true to UrlGeneratorInterface::ABSOLUTE_URI

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | symfony/symfony#16991

This was forgotten in #6009

Commits
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ec53faa Updated third param true to UrlGeneratorInterface::ABSOLUTE_URl in text Generating Absolute URLs

Author: xabbuh

book/routing.rst

@@ -1477,7 +1477,7 @@ Generating Absolute URLs
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
 By default, the router will generate relative URLs (e.g. ``/blog``). From
-a controller, simply pass ``true`` to the third argument of the ``generateUrl()``
+a controller, simply pass ``UrlGeneratorInterface::ABSOLUTE_URL`` to the third argument of the ``generateUrl()``
 method::
 
     use Symfony\Component\Routing\Generator\UrlGeneratorInterface;