Improve warning when saving g-code before slicing

This terminology is more consistent with what the rest of the interface uses.

Discovered during work on #4112.

plugins/GCodeWriter/GCodeWriter.py

@@ -70,7 +70,7 @@ class GCodeWriter(MeshWriter):
         active_build_plate = Application.getInstance().getMultiBuildPlateModel().activeBuildPlate
         scene = Application.getInstance().getController().getScene()
         if not hasattr(scene, "gcode_dict"):
-            self.setInformation(catalog.i18nc("@warning:status", "Please generate G-code before saving."))
+            self.setInformation(catalog.i18nc("@warning:status", "Please prepare G-code before exporting."))
             return False
         gcode_dict = getattr(scene, "gcode_dict")
         gcode_list = gcode_dict.get(active_build_plate, None)
@@ -86,7 +86,7 @@ class GCodeWriter(MeshWriter):
                 stream.write(settings)
             return True
 
-        self.setInformation(catalog.i18nc("@warning:status", "Please generate G-code before saving."))
+        self.setInformation(catalog.i18nc("@warning:status", "Please prepare G-code before exporting."))
         return False
 
     ##  Create a new container with container 2 as base and container 1 written over it.