Do not show gcode.gz as an option in save file dialog

CURA-5649

cura/CuraApplication.py

@@ -215,7 +215,6 @@ class CuraApplication(QtApplication):
 
         self._message_box_callback = None
         self._message_box_callback_arguments = []
-        self._preferred_mimetype = ""
         self._i18n_catalog = None
 
         self._currently_loading_files = []
@@ -514,9 +513,6 @@ class CuraApplication(QtApplication):
         self.applicationShuttingDown.connect(self.saveSettings)
         self.engineCreatedSignal.connect(self._onEngineCreated)
 
-        self.globalContainerStackChanged.connect(self._onGlobalContainerChanged)
-        self._onGlobalContainerChanged()
-
         self.getCuraSceneController().setActiveBuildPlate(0)  # Initialize
 
         CuraApplication.Created = True
@@ -997,30 +993,14 @@ class CuraApplication(QtApplication):
             self._camera_animation.setTarget(Selection.getSelectedObject(0).getWorldPosition())
             self._camera_animation.start()
 
-    def _onGlobalContainerChanged(self):
-        if self._global_container_stack is not None:
-            machine_file_formats = [file_type.strip() for file_type in self._global_container_stack.getMetaDataEntry("file_formats").split(";")]
-            new_preferred_mimetype = ""
-            if machine_file_formats:
-                new_preferred_mimetype =  machine_file_formats[0]
-
-            if new_preferred_mimetype != self._preferred_mimetype:
-                self._preferred_mimetype = new_preferred_mimetype
-                self.preferredOutputMimetypeChanged.emit()
-
     requestAddPrinter = pyqtSignal()
     activityChanged = pyqtSignal()
     sceneBoundingBoxChanged = pyqtSignal()
-    preferredOutputMimetypeChanged = pyqtSignal()
 
     @pyqtProperty(bool, notify = activityChanged)
     def platformActivity(self):
         return self._platform_activity
 
-    @pyqtProperty(str, notify=preferredOutputMimetypeChanged)
-    def preferredOutputMimetype(self):
-        return self._preferred_mimetype
-
     @pyqtProperty(str, notify = sceneBoundingBoxChanged)
     def getSceneBoundingBoxString(self):
         return self._i18n_catalog.i18nc("@info 'width', 'depth' and 'height' are variable names that must NOT be translated; just translate the format of ##x##x## mm.", "%(width).1f x %(depth).1f x %(height).1f mm") % {'width' : self._scene_bounding_box.width.item(), 'depth': self._scene_bounding_box.depth.item(), 'height' : self._scene_bounding_box.height.item()}