wifi: optimize WifiPpdu destructor

src/wifi/model/wifi-ppdu.cc

@@ -100,15 +100,6 @@ WifiPpdu::WifiPpdu(const WifiConstPsduMap& psdus,
     m_psdus = psdus;
 }
 
-WifiPpdu::~WifiPpdu()
-{
-    for (auto& psdu : m_psdus)
-    {
-        psdu.second = nullptr;
-    }
-    m_psdus.clear();
-}
-
 const WifiTxVector&
 WifiPpdu::GetTxVector() const
 {

src/wifi/model/wifi-ppdu.h

@@ -9,6 +9,7 @@
 #ifndef WIFI_PPDU_H
 #define WIFI_PPDU_H
 
+#include "wifi-psdu.h"
 #include "wifi-tx-vector.h"
 
 #include "ns3/nstime.h"
@@ -29,7 +30,6 @@ namespace ns3
 {
 
 class Packet;
-class WifiPsdu;
 class WifiPhyOperatingChannel;
 
 /**
@@ -73,7 +73,7 @@ class WifiPpdu : public SimpleRefCount<WifiPpdu>
     /**
      * Destructor for WifiPpdu.
      */
-    virtual ~WifiPpdu();
+    virtual ~WifiPpdu() = default;
 
     /**
      * Get the TXVECTOR used to send the PPDU.