fix: remove FunctionGeneration reference

When the model data is not available, the error message that was
generated was still using the removed `FunctionGeneration` module. This
has now been fixed.

src/model-data-io.jl

@@ -239,7 +239,7 @@ mkdir_if_not_exists(path) = !ispath(path) && mkdir(path)
 
 function ensure_model_data(M::Type)
     if !_is_model_data_downloaded(M)
-        @warn "Model data for $(FunctionGeneration.model_base_name(M)) is not present!\nRequisite model data may be fetched with `SpectralFitting.download_model_data($(FunctionGeneration.model_base_name(M)))`."
+        @warn "Model data for $(Base.typename(M).name) is not present!\nRequisite model data may be fetched with `SpectralFitting.download_model_data($(Base.typename(M).name))`."
         error("Missing data.")
     end
 end