Update installation-section of docs #1474
Description
The installation section is no longer up to date: https://docs.pulpproject.org/pulp_ansible/installation.html. We advise using the container-based installation.
It is sufficient to reference the required installation steps from pulpcore or pulpproject.org. There will be just a single source of truth eventually.
This is what we did for pulp_container: pulp/pulp_container@0c714b8.
See pulp/pulpcore#3888 for more details.