readme has outdated info

[charliemirabile]

• we should recommend using podman-compose down -v to remove volumes instead of pruning so we can avoid disclaimer about other dangling volumes
• podman-compose does handle overrides from environment properly so section 6 can be cleaned up a decent amount
• I am pretty sure the curl-minimal as default stuff is not true, and even if it were, the proper fix is dnf swap libcurl-minimal libcurl-full