[C++] Remove unnecessary #include

Was added in 29b9b7470cc33c2b7c4264f254335d788ef04c26
diff --git a/symtab.cc b/symtab.cc
index edb6752..b47522b 100644
--- a/symtab.cc
+++ b/symtab.cc
@@ -18,8 +18,6 @@
 
 #include "symtab.h"
 
-#include <iostream>
-
 #ifdef ENABLE_TID_CHECK
 #include <pthread.h>
 #endif