event/SocketMonitor: remove unused method Abandon()

src/event/SocketMonitor.cxx

@@ -64,15 +64,6 @@ SocketMonitor::Steal() noexcept
 }
 
 void
-SocketMonitor::Abandon() noexcept
-{
-	assert(IsDefined());
-
-	loop.Abandon(std::exchange(fd, SocketDescriptor::Undefined()).Get(),
-		     *this);
-}
-
-void
 SocketMonitor::Close() noexcept
 {
 	Steal().Close();

src/event/SocketMonitor.hxx

@@ -91,11 +91,6 @@ public:
 	 */
 	SocketDescriptor Steal() noexcept;
 
-	/**
-	 * Somebody has closed the socket.  Unregister this object.
-	 */
-	void Abandon() noexcept;
-
 	void Close() noexcept;
 
 	unsigned GetScheduledFlags() const noexcept {