Don't keep a separate use_legacy_network which is error-prone. Always infer from installed plugin version. (OrcaSlicer/OrcaSlicer#14441)

src/slic3r/GUI/GUI_App.hpp

@@ -742,6 +742,7 @@ public:
     int             install_plugin(std::string name, std::string package_name, InstallProgressFn pro_fn = nullptr, WasCancelledFn cancel_fn = nullptr);
     std::string     get_http_url(std::string country_code, std::string path = {});
     std::string     get_model_http_url(std::string country_code);
+    bool            use_legacy_network_plugin() const;
     bool            is_compatibility_version();
     bool            check_networking_version();
     void            cancel_networking_install();