Update Argo to 2.1.8

Package Merge Request

Package Changes

Update Argo to 2.1.8, latest chart for 2.1.x images.

Package MR

https://repo1.dso.mil/platform-one/big-bang/apps/core/argocd/-/merge_requests/58

For Issue

Closes https://repo1.dso.mil/platform-one/big-bang/apps/core/argocd/-/issues/34