[9.1] Passing a command as string when creating a "Symfony\Component\Process\Process" instance is deprecated since Symfony 4.2

New deprecation at core 9.1

  4x: Passing a command as string when creating a "Symfony\Component\Process\Process" instance is deprecated since Symfony 4.2, pass it as an array of its arguments instead, or use the "Process::fromShellCommandline()" constructor if you need features provided by the shell.

    3x in SchedulerDrushTest::testDrushCronMessages from Drupal\Tests\scheduler\Functional
    1x in SchedulerDrushTest::testDrushCronPublishing from Drupal\Tests\scheduler\Functional