[simple-scan] Add context to translation strings

[Robert Ancell <rancell src gnome org>]

commit 5c7b90312fab07987a3852da296fe2519e5304ca
Author: Robert Ancell <robert ancell canonical com>
Date:   Thu Feb 7 14:55:18 2019 +1300

    Add context to translation strings
    
    Fixes !89

 src/app-window.vala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/app-window.vala b/src/app-window.vala
index 27701f7..ab3e14d 100644
--- a/src/app-window.vala
+++ b/src/app-window.vala
@@ -970,7 +970,7 @@ public class AppWindow : Gtk.ApplicationWindow
         dialog.modal = true;
         dialog.border_width = 12;
         /* Title of dialog to reorder pages */
-        dialog.title = _("Reorder Pages");
+        dialog.title = C_("dialog title", "Reorder Pages");
         dialog.set_transient_for (this);
         dialog.key_press_event.connect ((e) =>
         {
@@ -1531,7 +1531,7 @@ public class AppWindow : Gtk.ApplicationWindow
         var section = new Menu ();
         gear_menu.append_section (null, section);
         section.append (_("Email"), "app.email");
-        section.append (_("Reorder Pages"), "app.reorder");
+        section.append (C_("menu", "Reorder Pages"), "app.reorder");
         section = new Menu ();
         gear_menu.append_section (null, section);
         section.append (_("Preferences"), "app.preferences");