Upgrade to System.Text.Json >= 8.0.5 once downlevel VS releases can handle it

[erikmav]

We need to downgrade to insecure 8.0.4 to avoid breaking use of the SDK packages in downlevel Visual Studio versions. This item tracks upgrading to something newer once we have a solution from the VS team.

Internal MS link for issue: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2295771?src=WorkItemMention&src-action=artifact_link