Harvest should disable the qtree template by default

[cgrinds]

Several customers have reported ONTAP slowdowns when collecting a large number of qtree objects. By default, it would be better to disable this template and provide instructions in the Qtree dashboard on how to re-enable if needed.

Also we need to fix the documentation for https://netapp.github.io/harvest/24.11.1/ontap-metrics/#quota_disk_limit which incorrectly states that the quota metrics come from the qtree.yaml template.