This reverts commit 3ae6aa0e4d.
If "group_id = 0" really did mean a diagnostic not from a language
server then various methods related to diagnostic set would need to be
updated. Something like [this
diff](https://gist.github.com/mgsloan/e902153bcaec207b39260a8f40d3134d).
Plan instead is to use InfoPopover instead of DiagnosticPopover for
these.
Release Notes:
- N/A
d83f1e8f8f