[cleanup] Remove useless includes.

Manual cleanup guided by include-what-you-use diagnostic.

Bug: webrtc:8311
Change-Id: I00be03392cc7ee005101427ea7dc701621ccea68
Reviewed-on: https://webrtc-review.googlesource.com/c/103320
Commit-Queue: Yves Gerey <yvesg@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25013}
diff --git a/rtc_base/nethelpers.cc b/rtc_base/nethelpers.cc
index b1221c3..81cd1af 100644
--- a/rtc_base/nethelpers.cc
+++ b/rtc_base/nethelpers.cc
@@ -25,10 +25,9 @@
 #endif
 #endif  // defined(WEBRTC_POSIX) && !defined(__native_client__)
 
-#include "rtc_base/byteorder.h"
-#include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/signalthread.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"  // for signal_with_thread...
 
 namespace rtc {