Fix broken links to openservicemesh/osm docs

[shashankram]

References to the following links are broken:

https://github.com/openservicemesh/osm/blob/main/docs/upgrade_guide.md#crd-upgrades (

osm-azure/docs/update-extension.md

Line 9 in d64f178

Please refer to the [OSM CRD Upgrades documentation](https://github.com/openservicemesh/osm/blob/main/docs/upgrade_guide.md#crd-upgrades) to prep your cluster for such an upgrade. After deleting your CRDs per the OSM documentation, please follow the upgrade [instructions](#instructions) in this guide instead of using Helm or the OSM CLI.

)

https://github.com/openservicemesh/osm/blob/main/docs/uninstallation_guide.md (

osm-azure/docs/delete-extension.md

Line 11 in d64f178

See the [OSM uninstallation guide](https://github.com/openservicemesh/osm/blob/main/docs/uninstallation_guide.md) for more details on which resources are cleaned up and which resources remain after cleanup.

)