Update Drupal Extension

[danepowell]

Is your feature request related to a problem? Please describe.
via Slack, blt-require-dev depends on drupal-extension 3.x, which depends on a version of Drupal Driver with a vulnerability.

Describe the solution you'd like
Updating Drupal Extension to 4.x might also update Drupal Driver and fix the vulnerability, we need to confirm that.

Describe alternatives you've considered
Individual users can stop using blt-require-dev and pull in the dependencies manually, or possibly use Composer aliases to use a newer version of Drupal Driver / Drupal Extension than what BLT requires.

[danepowell]

We already use Drupal Extension 4.x in BLT 12 so I think it's safe to update.