Remove dead legacy GLFW retained state

src/platform_windows/windows_runtime_shell.cpp

@@ -19,6 +19,7 @@ namespace {
 struct RetainedMainWindowSessionState final {
     HWND handle{};
     wchar_t title[512]{};
+    POINT last_point{};
     bool sandboxed = false;
 };
 
@@ -169,6 +170,16 @@ void set_main_window_sandboxed(bool sandboxed) noexcept
     retained_main_window_session_state().sandboxed = sandboxed;
 }
 
+POINT main_window_last_point() noexcept
+{
+    return retained_main_window_session_state().last_point;
+}
+
+void set_main_window_last_point(POINT point) noexcept
+{
+    retained_main_window_session_state().last_point = point;
+}
+
 int run_main_application(int argc, char** argv)
 {
     const auto instance = GetModuleHandle(NULL);