[ld2450] Use a user provided default constructor for RestartButton (#19183)

esphome/components/ld2450/button/restart_button.h

@@ -7,7 +7,8 @@ namespace esphome::ld2450 {
 
 class RestartButton : public button::Button, public Parented<LD2450Component> {
  public:
-  RestartButton() = default;
+  // User provided, not "= default": `new(p) RestartButton()` would zero-fill .bss that is already zero.
+  RestartButton() {}
 
  protected:
   void press_action() override;