lint: enable intrange linter (#7331)

Enable intrange linter to enforce modern Go range syntax over
traditional for loops, by converting:

for i := 0; i < n; i++

to:

for i := range n

Adding type conversions where needed for compatibility
with existing uint64 parameters.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

plugin/transfer/notify.go

@@ -41,7 +41,7 @@ func sendNotify(c *dns.Client, m *dns.Msg, s string) error {
 	var err error
 
 	code := dns.RcodeServerFailure
-	for i := 0; i < 3; i++ {
+	for range 3 {
 		ret, _, err := c.Exchange(m, s)
 		if err != nil {
 			continue