Rancher Hotfix builds: remove the necessity of cherry-picking commits

[moio]

At the moment the hotfix building instructions require to cherry-pick a commit in order to build Prime-only hotfixes of non-Prime versions of Rancher:

https://github.com/rancherlabs/rancher-process/blob/main/docs/documentation/howtos/rancher_hotfix_image_creation.md#to-avoid-pushing-images-to-dockerhub

Ideally, this step could be removed to make it easier to build hotfixes.