wifi: Fix condition for aborting RX when starting TX

The end time of the current reception cannot be later than now plus the delay
until idle (the delay until idle is at least the delay until reception ends),
hence the current reception is not aborted when TX starts while receiving a
PPDU payload.

src/wifi/model/wifi-phy.cc

@@ -1770,9 +1770,7 @@ WifiPhy::Send(WifiConstPsduMap psdus, const WifiTxVector& txVector)
     {
         noEndPreambleDetectionEvent &= it.second->NoEndPreambleDetectionEvents();
     }
-    if (!noEndPreambleDetectionEvent ||
-        (m_currentEvent &&
-         (m_currentEvent->GetEndTime() > (Simulator::Now() + m_state->GetDelayUntilIdle()))))
+    if (!noEndPreambleDetectionEvent || m_currentEvent)
     {
         AbortCurrentReception(RECEPTION_ABORTED_BY_TX);
     }