* canonicized rollbacks.md
* canonicized troubleshooting.md
* canonicized upgrades.md
there were two corresponding pages for 2.0-2.4, one for helm 2 and one for helm 3, so i added canonical refs for both
* canonicized feature-flags
2.0-2.4 and 2.5 pages were in different folders
* corrected url on feature flags
* canonicized air-gapped-upgrades
the 2.0-2.4 doc structure is kind of wonky but the closest match was section 3 in install-rancher-ha.md, 'Render the Rancher Helm Template'
* canonicized rancher-on-aks
there is no good match for 2.0-2.4
the best match corresponds to a quickstart guide in the other versions
* canonicized rancher-on-amazon-eks
nothing similar in 2.0-2.4
* canonicized rancher-on-gke
no corresponding 2.0-2.4 page
* corrected page
