System package list for tar installation is out of date

[cmcgee1024]

Describe the bug

When going to this page on the website: http://swift.org/install/linux/tarball

And visiting the Ubuntu 20.04 section. The list of packages doesn't include these packages:

unzip libcurl4-openssl-dev libpython3.8 libxml2-dev

Note that the equivalent Dockerfile for the official swift lists these packages as required here for 6.1:

https://github.com/swiftlang/swift-docker/blob/main/6.1/ubuntu/20.04/Dockerfile

Expected behavior

It's expected that the list of required system packages agree between swiftly, the docker files for official swift images, and the website.

Actual behavior

There is a discrepancy between package lists.