This PR was merged into the 4.4 branch.

Discussion
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[FrameworkBundle] conflict with VarDumper < 4.4

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

While trying FrameworkBundle 4.4.x-dev I noticed that I was still using VarDumper 4.3 which leads to this error:

```
> app/console cache:clear

Fatal error: Uncaught Symfony\Component\ErrorHandler\Exception\ClassNotFoundException: Attempted to load class "ContextualizedDumper" from namespace "Symfony\Component\VarDumper\Dumper".
Did you forget a "use" statement for another namespace? in /var/www/x/symfony/app/cache/dev/ContainerB7mbdCh/getDebug_DumpListenerService.php:13
Stack trace:
#0 /var/www/x/symfony/app/cache/dev/ContainerB7mbdCh/appAppKernelDevDebugContainer.php(1357): require()
#1 /var/www/x/symfony/app/cache/dev/ContainerB7mbdCh/appAppKernelDevDebugContainer.php(2282): ContainerB7mbdCh\appAppKernelDevDebugContainer->load('getDebug_DumpLi...')
#2 /var/www/x/symfony/vendor/symfony/event-dispatcher/EventDispatcher.php(275): ContainerB7mbdCh\appAppKernelDevDebugContainer->ContainerB7mbdCh\{closure}()
#3 /var/www/x/symfony/vendor/symfony/event-dispatcher/EventDispatcher.php(90): Symfony\Component\EventDispatcher\EventDispatcher->sortListeners('console.command')
#4 /var/www/x in /var/www/x/symfony/app/cache/dev/ContainerB7mbdCh/getDebug_DumpListenerService.php on line 13
PHP Fatal error:  Uncaught Symfony\Component\ErrorHandler\Exception\ClassNotFoundException: Attempted to load class "ContextualizedDumper" from namespace "Symfony\Component\VarDumper\Dumper".
Did you forget a "use" statement for another namespace? in /var/www/x/symfony/app/cache/dev/ContainerB7mbdCh/getDebug_DumpListenerService.php:13
Stack trace:
#0 /var/www/x/symfony/app/cache/dev/ContainerB7mbdCh/appAppKernelDevDebugContainer.php(1357): require()
#1 /var/www/x/symfony/app/cache/dev/ContainerB7mbdCh/appAppKernelDevDebugContainer.php(2282): ContainerB7mbdCh\appAppKernelDevDebugContainer->load('getDebug_DumpLi...')
#2 /var/www/x/symfony/vendor/symfony/event-dispatcher/EventDispatcher.php(275): ContainerB7mbdCh\appAppKernelDevDebugContainer->ContainerB7mbdCh\{closure}()
#3 /var/www/x/symfony/vendor/symfony/event-dispatcher/EventDispatcher.php(90): Symfony\Component\EventDispatcher\EventDispatcher->sortListeners('console.command')
#4 /var/www/x in /var/www/x/symfony/app/cache/dev/ContainerB7mbdCh/getDebug_DumpListenerService.php on line 13
Script app/console cache:clear handling the post-update-cmd event returned with error code 255
```
So we need to use `symfony/var-dumper >= 4.4`

Commits
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9b512c6 [FrameworkBundle] conflict with VarDumper < 4.4