Remove now-unnecessary poll, fcntl includes from net(base).cpp

As far as I can tell, the code calling for these includes was removed in:
6e68ccbefe #24356
82d360b5a8 #21387

src/netbase.cpp

@@ -21,14 +21,6 @@
 #include <limits>
 #include <memory>
 
-#ifndef WIN32
-#include <fcntl.h>
-#endif
-
-#ifdef USE_POLL
-#include <poll.h>
-#endif
-
 // Settings
 static GlobalMutex g_proxyinfo_mutex;
 static Proxy proxyInfo[NET_MAX] GUARDED_BY(g_proxyinfo_mutex);