* 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