[Producer] Fix input_name to return empty list.

include/aidge/operator/Producer.hpp

@@ -133,7 +133,7 @@ public:
     inline IOIndex_t nbDataInputs() const noexcept override final { return 0; };
     inline IOIndex_t nbOutputs() const noexcept override final { return 1; };
     static const std::vector<std::string> getInputsName(){
-        return {""};
+        return {};
     }
     static const std::vector<std::string> getOutputsName(){
         return {"data_output"};