Delete/disable saving of .mat files after pipeline has finished

[KTZ228]

Since users might not need to use the raw .mat files after the pipeline is finished, they can add extra clutter to the output.
And more importantly, since you're saving raw output these files take up a large part of the storage quota.

So, my suggestion would be to delete these files after the pipeline has finished by default to save storage and remove clutter for most normal users.