Clean up old images

https://uab-rc.slack.com/archives/C9YB78YSX/p1705590875167869

Ops team pointed out that there are a bunch of image artifacts, mostly from the knightly pipeline. Notice that the OOD pipeline should've cleaned up the old image, but it doesn't seem to work. Further investigation shows that we did not update the grep pattern when we updated the timestamp to look like RCF3339. (!65 (22e8f3ff))