PSA re: utz' engine downloads

As of today, individual downloads for my Speccy engines are no longer available from the github repo. You can now grab all the converters etc. as a single download on the Releases page.

The reason for this change is that I intend to use the github repo as a submodule for MDAL/Bintracker at some point, and having a large number of binary files in the repo is somewhat counter-productive in that respect. My apologies for any inconvenience caused.