Adopt suggestion by @tkoeppe:

* #4877 (comment)

* https://godbolt.org/z/Wa79nKz6e

Author: rwgk

include/pybind11/numpy.h

@@ -71,6 +71,13 @@ class LazyInitializeAtLeastOnceDestroyNever {
         PYBIND11_WARNING_POP
     }
 
+    constexpr LazyInitializeAtLeastOnceDestroyNever() = default;
+#if __cplusplus >= 202002L
+    constexpr
+#endif // C++20
+        ~LazyInitializeAtLeastOnceDestroyNever()
+        = default;
+
 private:
     alignas(T) char value_storage_[sizeof(T)];
     bool initialized_ = false;