SS- spreadsheets dates as data starting point

### How could the content be improved?

Toby asked a question about [this episode](https://datacarpentry.github.io/spreadsheets-socialsci/03-dates-as-data.html) in #1943

That episode does not have clear demonstration to me. I can sort of see what someone might do to live demonstrate this episode, but I could also imagine a person not demonstrating anything, but not being able to justify that they did not follow the curriculum.

I think we should remove this episode to avoid anyone being in that position.

### Which part of the content does your suggestion apply to?

https://carpentries.github.io/instructor-training/demo_lessons.html#dc-socialsci

Review the DC Social Sci section of the demo_lessons page and the linked dates-as-data episode, using issue #1943 for context. Done means the episode is removed from the instructor-training demonstration guidance and the page accurately reflects the remaining curriculum.

Written by the indexing model from the issue text.