Remove Spectrum Files (Reminder)

[drojf]

This is a reminder to remove the Spectrum files from the voice? archive, as they are no longer required.

I would do it immediately, but the new DLL has only just been released, and there may be some bugs which require us to revert to the previous version.

Once we're sure there are no major bugs, we can delete the spectrum files.

Removing spectrum files will speed up install times on Windows since it doesn't handle lots of small files very well.