add comment on contact tracing including non-cases

use https://epiverse-trace.github.io/simulist/articles/vis-linelist.html#subset-contact-network-to-transmission-network

at:

https://github.com/epiverse-trace/tutorials-middle/blob/6854f93160a9cb42c5e94dad05bd27f6b6eea6ae/episodes/superspreading-estimate.Rmd#L188-L208

Open episodes/superspreading-estimate.Rmd around lines 188-208 and compare the linked simulist guidance on reducing a contact network to a transmission network. Add the requested comment about contact tracing that includes non-cases at that location, then verify the tutorial source remains valid.

Written by the indexing model from the issue text.