Update Structure of CLDT image

[sstevens2]

How could the content be improved?

When we feel the curriculum has settled in rearrangements, we should update the Structure of CLDT image in the intro episode. I realized when teaching it yesterday that we don't start to teach infrastructure until the 3rd half day and then we integrate them after that.

Which part of the content does your suggestion apply to?

https://carpentries.github.io/lesson-development-training/introduction.html

[tobyhodges]

Based on discussion at today's Maintainers meeting, I think we should take care of this before we mark the lesson as stable and make the next release