codec: drop unused _shutdownEvent

using epicsThread::exitWait() instead

src/remote/codec.cpp

@@ -1142,8 +1142,6 @@ void BlockingTCPTransportCodec::receiveThread()
                 __FILE__, __LINE__);
         }
     }
-
-    this->_shutdownEvent.signal();
 }
 
 

src/remote/pv/codec.h

@@ -457,7 +457,6 @@ protected:
 private:
     AtomicValue<bool> _isOpen;
     epics::pvData::Thread _readThread, _sendThread;
-    epics::pvData::Event _shutdownEvent;
     const SOCKET _channel;
 protected:
     osiSockAddr _socketAddress;