Remove deprecated overrides of rtc::Thread.

PostAt and ReceiveSends are about to be removed from rtc::Thread,
removing overrides to avoid compile error.

Bug: webrtc:9883
Change-Id: I753fca76b07f5c82b1358f7fa3c4aadd661ecb5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2000759Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Sebastian Jansson <srte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732805}

jingle/glue/thread_wrapper.cc

@@ -307,18 +307,6 @@ bool JingleThreadWrapper::Peek(rtc::Message*, int) {
   return false;
 }
 
-void JingleThreadWrapper::PostAt(const rtc::Location& posted_from,
-                                 uint32_t,
-                                 rtc::MessageHandler*,
-                                 uint32_t,
-                                 rtc::MessageData*) {
-  NOTREACHED();
-}
-
-void JingleThreadWrapper::ReceiveSends() {
-  NOTREACHED();
-}
-
 int JingleThreadWrapper::GetDelay() {
   NOTREACHED();
   return 0;

jingle/glue/thread_wrapper.h

@@ -97,12 +97,6 @@ class JingleThreadWrapper
   void Restart() override;
   bool Get(rtc::Message* message, int delay_ms, bool process_io) override;
   bool Peek(rtc::Message* message, int delay_ms) override;
-  void PostAt(const rtc::Location& posted_from,
-              uint32_t timestamp,
-              rtc::MessageHandler* handler,
-              uint32_t id,
-              rtc::MessageData* data) override;
-  void ReceiveSends() override;
   int GetDelay() override;
 
   // rtc::Thread overrides.