Fix 2.x branch integration with AI 2.x now that Symfony Platform is integrated
# Problem/motivation
Tests now fail because of #3574187
## Steps to reproduce
E.g. run `ddev exec ./vendor/bin/phpunit -c core/phpunit.xml.dist modules/contrib/ai_search/tests/src/Functional/AiSearchSetupMySqlTest.php --filter=testContentIndexingCompleted`
# Proposed resolution
- Update AI Search compatibility with AI Core 2.x branch
- Document any breaking changes needed in VDB Providers
issue