Lab 2 - clarify issues with possible port 5000 in use errors for demo application

Getting issues with port in use:

$ podman run -p 5000:5000 hello-otel:latest

Error: preparing container 33db8dcddc840b3a83bb16baad60600aeb315090ddf9b5e1903b3d906fd1d3c6 for attach: something went wrong with the request: "listen tcp :5000: bind: address already in use\n"

Sure you can redo the docker file to use a different port, and also start container with different port, but should address the possibility in the slide here: https://o11y-workshops.gitlab.io/workshop-opentelemetry/lab02.html#/7

Might be handy to mention it in the intro-to-instrumentation demo app README.md file.