This reverts commit c75898cd6a.
Airship 2 ended up using the Flux helm-controller instead:
https://github.com/fluxcd/helm-controller
So this is no longer needed. Removing it to get rid of tech
debt to ease introduction of Helm 3 support.
This retains the part of the commit which extracts the
chart download logic to its own handler as this is still useful.
Change-Id: Icb468be2d4916620fd78df250fd038ab58840182
5f1ffbbbbe