labels: improve comment on Builder.Set
@@ -468,7 +468,7 @@ Outer:
return b
}
-// Set the name/value pair as a label.
+// Set the name/value pair as a label. A value of "" means delete that label.
func (b *Builder) Set(n, v string) *Builder {
if v == "" {
// Empty labels are the same as missing labels.
