Use DI not \Drupal in src/Plugin/views/filter/AdministrativeArea.php

I am honestly fine with just modifying the constructor. It's our own views plugin, if you decide to override that one then you can keep it up to date.

But I know maintainers have gotten more cautious over the past few years.

If there were lots of benefit to end users to "rip off the bandaid" I would consider it. But this is basically for a hypothetical improvement in the unit-testability of a class that we're not unit testing directly. I'd rather not introduce possible disruption and pain for this, since it's a "fix" to a non-bug that no one will ever notice we've "improved". 😂 Hence my desire to be a bit more cautious and jump through a few more hoops to solve this.