Remove old thread_local.h

This was to work around a clang 9.0.0 bug.  We are on clang 13.  Make
things simpler by removing it.

Change-Id: I4bad16270795bb82b8c498146a4bf7388565a1c7
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/realtime.cc b/aos/realtime.cc
index 94dfa4e..22b864e 100644
--- a/aos/realtime.cc
+++ b/aos/realtime.cc
@@ -18,7 +18,6 @@
 #include "glog/logging.h"
 #include "glog/raw_logging.h"
 
-#include "aos/thread_local.h"
 #include "aos/uuid.h"
 
 DEFINE_bool(
@@ -229,7 +228,7 @@
 namespace {
 // Bool to track if malloc hooks have failed to be configured.
 bool has_malloc_hook = true;
-AOS_THREAD_LOCAL bool is_realtime = false;
+thread_local bool is_realtime = false;
 }  // namespace
 
 bool MarkRealtime(bool realtime) {