[DOCS] Provide upgrade notes for openmetadata/ingestion docker image with 0.12.1

[akash-jain-10]

Is some content missing, wrong or not clear?

Describe the solution you'd like Call out in OpenMetadata Docs for the breaking change of centralising openmetadata/ingestion docker image and deprecation of openmetdata/airflow image on K8s Helm Charts. Call out environment variables name updates, ingestion volume updates in docker-compose.yml.

Additional context Add any other context or screenshots about the feature request here.