feat: keep version check in MSIX build, point update dialog at the Store

The update check is notification-only (OrcaSlicer never auto-downloads),
so the Store build keeps checking for new versions instead of skipping
the check. What changes when packaged is the new-version dialog: the
Download button is hidden, the info text asks the user to update from
the Microsoft Store, and the hyperlink / wxID_YES action opens the Store
product page instead of the GitHub release page.

src/slic3r/GUI/MainFrame.cpp

@@ -2577,10 +2577,7 @@ static wxMenu* generate_help_menu()
     // Check New Version
     append_menu_item(helpMenu, wxID_ANY, _L("Check for Updates"), _L("Check for Updates"),
         [](wxCommandEvent&) {
-            if (is_running_in_msix())
-                open_ms_store_product_page();
-            else
-                wxGetApp().check_new_version_sf(true, 1);
+            wxGetApp().check_new_version_sf(true, 1);
         }, "", nullptr, []() {
             return true;
         });