GitLabCI: Fix existing PHPStan issues

Created MR !15 that:

• Adds a @phpstan-ignore comment in Drupal\config_distro\Form\ConfigDistroImportForm to ignore error about extending an internal class since we are knowingly doing so.
• Removes code for supporting Drupal core <8.6 since the 2.0.x branch no longer supports D8 (see [#https://www.drupal.org/project/config_distro/issues/3000886]).

I also created a separate issue for exploring alternative implementations for ConfigDistroImportForm that don't require extending an internal class ( 📌 Explore alternatives to extending internal core ConfigSync form class Active ).

This looks good to me RTBC

My only thought was that we could add a test to determine whether the proper events are fired, but that can be a follow-up or part of the " Create Rigorous Tests 📌 Create rigurous tests Needs review " ticket.

Merged.

Automatically closed - issue fixed for 2 weeks with no activity.