In T369709: Switch `GEUseCommunityConfigurationExtension` to `true` in extension.json, we switched (most) PHPUnit tests to use the CommunityConfiguration extension (rather than the legacy CC support). Within this tasks, we need to migrate all API tests in GrowthExperiments to also make use of Community Configuration 2.0. This is important to ensure our tests run with configuration reasonably similar to production, in case an issue is caused by the way how we integrate with the CommunityConfiguration extension or similar.
Credits to @Michael for thinking of this.