docs/WIP/Tutorial_DiscordMERLIN.ipynb is outdated

[NimaSarajpoor]

The notebook Tutorial_DiscordMERLIN.ipynb is outdated. For instance:

• It loads data from directories that do not exist. Also, the original data provided by authors in the MERLIN webpage is not accessible anymore.
• It uses some code from STUMPY that have been updated since then, and they are not backward compatible. For example, the notebook uses the code T, M_T, Σ_T = core.preprocess(ts, m); However, this function in branch main now returns four values instead of three.