That would be within Assets > Clavian > SuperTextMesh> Shaders > STMultra.shader by default, I believe. I'm just doing this by memory so I may be wrong...
By the way, this is assuming you're using the ultra shader to begin with... the same error may actually be on the universal shader too, so the shadow passes there can be removed as well. Those are within the "Universal" subfolder within the Shaders folder. Really sorry I can't just send a build at the moment, so I hope this helps!