Remove obsolete 'version' from docker-compose.yml

[trivikr]

Fixes: https://github.com/bluesky-social/social-app/issues/6535

No warning is shown

$ yarn e2e:mock-server                                             
yarn run v1.22.19
$ NODE_ENV=development ./jest/dev-infra/with-test-redis-and-db.sh ts-node --project tsconfig.e2e.json __e2e__/mock-server.ts
[+] Running 2/2
 ✔ Container dev-infra-redis_test-1  Healthy                                                                                                     1.1s 
 ✔ Container dev-infra-db_test-1     Healthy                                                                                                     1.6s 
Mock server manager listening on 1986