Merge pull request #366 from Maks-2012/patch-1

Fix preferIPOnlyIPv6

mtglib/internal/dc/telegram.go

 	case preferIPOnlyIPv4:
 		return t.view.getV4(dc)
 	case preferIPOnlyIPv6:
-		return t.view.getV4(dc)
+		return t.view.getV6(dc)
 	case preferIPPreferIPv4:
 		return append(t.view.getV4(dc), t.view.getV6(dc)...)
 	}