luci-app-ddns: Incorrect tooltip

[majaha]

If you click Edit on a ddns service and open the Timer Settings tab, the tooltip under Error Retry Interval is duplicated from the Error Retry Counter entry.

Probably the tooltip under Retry Unit should be moved under Error Retry Interval, and the Retry Unit tooltip should should read "Units for the Error Retry Interval"

[systemcrash]

This issue can be closed.