chore: upgrade to github.com/upper/db/v4 (#705)

* Upgrade to github.com/upper/db/v4

* fix(oonitest): repair imports after merge

Oops, okay, it seems the merge did not preserve all the import
changes, so let's ensure we use the right imports here!

* cleanup(go.mod): don't refer to upper.io/db/v3

These lines didn't disappear previously because the merge commit
failed to remove all references to upper.io/db/v3.

Co-authored-by: stergem <sgemelas@protonmail.com>
Co-authored-by: Simone Basso <bassosimone@gmail.com>

cmd/ooniprobe/internal/database/actions_test.go

@@ -8,7 +8,7 @@ import (
 	"os"
 	"testing"
 
-	db "upper.io/db.v3"
+	"github.com/upper/db/v4"
 )
 
 type locationInfo struct {