Ensure that default branch contains the recommended image

[ssbarnea]

Currently the default (main) branch of this repository uses an outdated container and this makes testing it much harder as new users will have to guess which branch to use.

As of writing this ticket, the active branch looks to be devspaces-3-rhel-9 but we need the main to always have the latest image, especially as this repository might be linked from documentation and blog post.