go.mod references incorrectly labeled Argo CD package

[jgwest]

Describe the bug

The current version of the go.mod appears to reference an extremely old version of Argo CD, but that has a modern timestamp:

	github.com/argoproj/argo-cd v0.8.1-0.20210326223336-719d6a9c252e

Fortunately, however, this is actually just v1.8.x release that was incorrectly tagged upstream, as you can see from the parent commits of that commit: https://github.com/argoproj/argo-cd/commits/719d6a9c252e93ffed1dc1732e3d2dead349fcbe

In any case, we should probably update to a newer v1.8.x release that has been properly tagged, or move up to v2.