Fix Redis service name

Pod: migrations

│ migrations - FAILED connecting to 'redis://gitlab-redis-master.selfsigned.svc:6379' from resque.yml, through gitlab-redis-master.selfsigned.svc                                            │
│ migrations ERROR: Error connecting to Redis on gitlab-redis-master.selfsigned.svc:6379 (SocketError) 

Pod: webservice

dependencies ERROR: Error connecting to Redis on gitlab-redis-master.selfsigned.svc:6379 (SocketError)                                                                                     │
│ dependencies - FAILED connecting to 'redis://gitlab-redis-master.self2021-02-17T22:24:16.115948837Z signed.svc:6379' from cable.yml, through gitlab-redis-master.selfsigned.svc            │
│ dependencies ERROR: Error connecting to Redis on gitlab-redis-master.selfsigned.svc:6379 (SocketError)2021-02-17T22:24:17.905972578Z                                                       │
│ dependencies Database Schema - current: 0, codebase: 20210115215854              

The pods are trying to reach redis at service name gitlab-redis-master, but the service name created by the Operator is just gitlab-redis.