Improve SurfaceTool::generate_tangents UV error message

Fixes #92395.

scene/resources/surface_tool.cpp

@@ -1158,7 +1158,7 @@ void SurfaceTool::mikktSetTSpaceDefault(const SMikkTSpaceContext *pContext, cons
 }
 
 void SurfaceTool::generate_tangents() {
-	ERR_FAIL_COND(!(format & Mesh::ARRAY_FORMAT_TEX_UV));
+	ERR_FAIL_COND_MSG(!(format & Mesh::ARRAY_FORMAT_TEX_UV), "UVs are required to generate tangents.");
 	ERR_FAIL_COND(!(format & Mesh::ARRAY_FORMAT_NORMAL));
 
 	SMikkTSpaceInterface mkif;