Remove jobs for Iron Irwini

[Yadunund]

Iron is now EOL.

Note: Marking this as draft until the final snapshots of Iron are captured.

[clalancette]

Just as an FYI, what we usually do here is to mark the jobs as "Disabled" on the buildfarm for a month or so. That way, if something catastrophic happens and we need to do another release, it is easy to turn on. After that, we usually merge a PR like this and delete the builds from the buildfarm.

Thus, while this is the correct thing to do, I suggest we hold off on merging this until at least January.

[Yadunund]

Sounds good. I'll leave it as draft until then.

[Yadunund]

We learnt that disabling jobs in the buildfarm is temporary and as long as these configs exist, the jobs will be re-created/enabled.

It's been over a month since Iron was marked as EOL and no issues have been reported. I've tagged the latest commit on this repo as iron-20250203-config.

This PR is ready for review / merge.

[clalancette]

Looks good to me, but let's wait to merge until @nuclearsandwich has had a chance to review.