Update search-admin config to reflect app changes

- Remove environment variable for `database_cleaner` configuration (this
  gem has been removed as we're not using Cucumber anymore and RSpec
  system tests run in transactions so don't need it)
- Change command in `app` stack to run conventional `bin/dev` that has
  been added to the application
- Add explicit port to `app` stack now that the application is run
  through Foreman
- Add `TEST_DATABASE_URL` to app stack to allow running tests on `app`
  stack too for convenience

projects/search-admin/docker-compose.yml

@@ -27,20 +27,20 @@ services:
       DATABASE_URL: "mysql2://root:root@mysql-8/search_admin_development"
       TEST_DATABASE_URL: "mysql2://root:root@mysql-8/search_admin_test"
       REDIS_URL: redis://redis
-      DATABASE_CLEANER_ALLOW_REMOTE_DATABASE_URL: "true"
 
   search-admin-app: &search-admin-app
     <<: *search-admin-base
     depends_on:
       - mysql-8
       - nginx-proxy
       - publishing-api-app
-      - search-api-app
     environment:
       DATABASE_URL: "mysql2://root:root@mysql-8/search_admin_development"
+      TEST_DATABASE_URL: "mysql2://root:root@mysql-8/search_admin_test"
       REDIS_URL: redis://redis
       VIRTUAL_HOST: search-admin.dev.gov.uk
       BINDING: 0.0.0.0
+      PORT: 3000
     expose:
       - "3000"
-    command: bin/rails s --restart
+    command: bin/dev