Go into Admin/Manage SNMP Collections and Data Collection Groups

In the SNMP Collections tab, select a collection you wish to remove. More collection detail information will appear. Click Delete. The collection verifies you want to remove it and it is gone.

However, data collection is still is attempted. This should work just like changing SNMP attributes for a node or creating a notification. It is not clear that this only affects the config and requires a restart (and IMO requiring a restart shouldn't be the solution).

Sample log after the config is removed is attached.