chore(evals): remove obsolete compose version key and set test env

- Remove 'version' key per compose v2 warning
- Keep NEXT_PUBLIC_CB_ENVIRONMENT=test for test stack

🤖 Generated with Codebuff
Co-Authored-By: Codebuff <noreply@codebuff.com>

Author: brandonkachen

evals/docker-compose.evals.yml

@@ -1,4 +1,3 @@
-version: '3.9'
 services:
   db:
     image: postgres:16-alpine
@@ -25,6 +24,7 @@ services:
     environment:
       DATABASE_URL: postgresql://codebuff:codebuff@db:5432/codebuff
       PORT: "4242"
+      NEXT_PUBLIC_CB_ENVIRONMENT: "test"
       NODE_ENV: production
     depends_on:
       db: