[IMPROVE] Update to MongoDB 4.0 in docker-compose file (#13396)

docker-compose.yml

@@ -23,7 +23,7 @@ services:
       - "traefik.frontend.rule=Host: your.domain.tld"
 
   mongo:
-    image: mongo:3.2
+    image: mongo:4.0
     restart: unless-stopped
     volumes:
      - ./data/db:/data/db
@@ -35,7 +35,7 @@ services:
   # this container's job is just run the command to initialize the replica set.
   # it will run the command and remove himself (it will not stay running)
   mongo-init-replica:
-    image: mongo:3.2
+    image: mongo:4.0
     command: 'mongo mongo/rocketchat --eval "rs.initiate({ _id: ''rs0'', members: [ { _id: 0, host: ''localhost:27017'' } ]})"'
     depends_on:
       - mongo