`AvoidDotImport` leaves dangling `Println`

[greg-at-moderne]

• TestAvoidDotImportRemoved — removing import . "fmt" leaves bare Println dangling (undefined: Println) and a now-unused "fmt". The fix needs to re-qualify references (Println → fmt.Println), which the unused-import pass (Fix recipes to remove unused imports #32) can’t do on its own.