minor #8879 [Process] remove deprecated ProcessBuilder (TomasVotruba)

This PR was merged into the 4.0 branch.

Discussion
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[Process] remove deprecated ProcessBuilder

Because this class doesn't exists in Symfony 4.0 anymore.
https://github.com/symfony/process/blob/f1a7a49ec22d7b6336b1c8b958c92e86923adcbb/CHANGELOG.md#400

I was surprised to look for it in my `/vendor/symfony/process` but unable to find :)

Commits
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d2c5767 [Process] remove deprecated ProcessBuilder

Author: weaverryan

components/process.rst

@@ -258,38 +258,6 @@ instead::
     );
     $process->run();
 
-To make your code work better on all platforms, you might want to use the
-:class:`Symfony\\Component\\Process\\ProcessBuilder` class instead::
-
-    use Symfony\Component\Process\ProcessBuilder;
-
-    $builder = new ProcessBuilder(array('ls', '-lsa'));
-    $builder->getProcess()->run();
-
-In case you are building a binary driver, you can use the
-:method:`Symfony\\Component\\Process\\ProcessBuilder::setPrefix` method to prefix all
-the generated process commands.
-
-The following example will generate two process commands for a tar binary
-adapter::
-
-    use Symfony\Component\Process\ProcessBuilder;
-
-    $builder = new ProcessBuilder();
-    $builder->setPrefix('/usr/bin/tar');
-
-    // '/usr/bin/tar' '--list' '--file=archive.tar.gz'
-    echo $builder
-        ->setArguments(array('--list', '--file=archive.tar.gz'))
-        ->getProcess()
-        ->getCommandLine();
-
-    // '/usr/bin/tar' '-xzf' 'archive.tar.gz'
-    echo $builder
-        ->setArguments(array('-xzf', 'archive.tar.gz'))
-        ->getProcess()
-        ->getCommandLine();
-
 Process Timeout
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