Update docs to consistently separate use of API and ingestion ports in Docker examples

[nblumhardt]

Originally suggested by @mloskot in #2515.

---

(The) port mapping examples in the docs e.g. -p 5341:80 may be confusing:

• Why not suggest the 'natural' mapping of -p 5341:5341?
• Why would I want to publish Seq API port 80 in container on 5341 port while that port is used in container as Seq ingestion port?

For those new to Seq, it would be clearer if the examples did not mix-up the ports and displayed the 'natural' mapping

• like -p 80:80 -p 5341:5341 or -p 8080:80 -p 5341:5341
• or -p 5341:5341 only
• or -p 5341:45341 only assuming user configures seq config set -k api.ingestionPort -v 45341

but not -p 5341:80 which is still used in number of places.

The generic example of -p $HOST_HTTP_PORT:80 -p $HOST_INGESTION_PORT:5341 also used in the docs is an improvement though.