Make phpStan happy

Problem/Motivation

There are currently three items that phpstan is not happy with in the CI pipeline. It would be good to get those resolved so we don't have to keep seeing them in every MR.

Line src/AiMigrator.php
------ ----------------------------------------------------------------------
66 \Drupal calls should be avoided in classes, use dependency injection
instead
🪪 globalDrupalDependencyInjection.useDependencyInjection
70 \Drupal calls should be avoided in classes, use dependency injection
instead
🪪 globalDrupalDependencyInjection.useDependencyInjection
99 \Drupal calls should be avoided in classes, use dependency injection
instead
🪪 globalDrupalDependencyInjection.useDependencyInjection

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes