Docs: Downgrade a ClusterExtension

[perdasilva]

Write user documentation describing how to downgrade a package.

A placeholder for the document has already been created in docs/drafts/Tasks/downgrading_an_extension.md.

For downgrades I think there are some specific overrides a user would need to put in place, namely:

• Ignoring the catalog provided upgrade constraints
• Disabling the CRD checks

[michaelryanpeter]

I think most of the content (besides disabling CRD checks) already exists here: https://github.com/operator-framework/operator-controller/blob/main/docs/drafts/upgrade-support.md#manually-verified-upgrades-and-downgrades

[michaelryanpeter]

@bentito ^

[bentito]

thanks @michaelryanpeter

[LalatenduMohanty]

Closing this as #1277 has merged