minor #16854 Fix development testing examples (gitomato)

This PR was merged into the 5.4 branch.

Discussion
----------

Fix development testing examples

<!--

If your pull request fixes a BUG, use the oldest maintained branch that contains
the bug (see https://symfony.com/releases for the list of maintained branches).

If your pull request documents a NEW FEATURE, use the same Symfony branch where
the feature was introduced (and `6.x` for features of unreleased versions).

-->

Commits
-------

3d1b667 Fix development testing examples

Author: javiereguiluz

controller/error_pages.rst

@@ -170,7 +170,7 @@ automatically when installing ``symfony/framework-bundle``):
             xsi:schemaLocation="http://symfony.com/schema/routing
                 https://symfony.com/schema/routing/routing-1.0.xsd">
 
-            <when env="prod">
+            <when env="dev">
                 <import resource="@FrameworkBundle/Resources/config/routing/errors.xml" prefix="/_error"/>
             </when>
         </routes>
@@ -181,7 +181,7 @@ automatically when installing ``symfony/framework-bundle``):
         use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;
 
         return function (RoutingConfigurator $routes) {
-            if ('dev' === $container->env()) {
+            if ('dev' === $routes->env()) {
                 $routes->import('@FrameworkBundle/Resources/config/routing/errors.xml')
                     ->prefix('/_error')
                 ;