Add links to removed obsolete sample projects.

[p-m-j]

I found it quite frustrating to be reading / watching training content that made reference to the Jetsurvey project in this repo only to find it no longer exists. I imagine this would be even more frustating for those going through learning materials alongside learning git.

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[IanGClifton]

Rebecca, can you verify these are the right hashes/links we want to use to point people to the projects we've removed?