Drop support for Drush v10 and Symfony before v6

[davereid]

This came from #451 that we cannot test the Renovate PRs with Symfony because it wants to update the lowest version, currently v3, which is only really supported for Drupal 8. Drupal 9 required v4, and Drupal 10.0 required v6.2 and the current 10.2 requires v6.4. What is our strategy for following core's recommended minimum dependencies for Drainpipe given this is a Drupal-focused project?

Drush v10 is also EOL and doesn't support Drupal 10 or PHP 8 at all: https://www.drush.org/12.x/install/#drupal-compatibility