Remove line causing container already existed (open-telemetry#27047)

Remove container naming so newly created container will not overlap
existing container on host.

**Description:** <Describe what has changed.>
Newly created container should have name generated automatically by
Docker compose, so that existing container with the same name will not
need to be deleted

**Link to tracking Issue:** <Issue number if applicable>

**Testing:** <Describe what testing was performed and which tests were
added.>

**Documentation:** <Describe the documentation added.>

examples/demo/docker-compose.yaml

@@ -59,7 +59,6 @@ services:
  - otel-collector
 
  prometheus:
- container_name: prometheus
  image: prom/prometheus:latest
  restart: always
  volumes: