Remove duplicate TLS define from kist code.

Duplicate comes from introducing this define into 0.2.9, which did not yet
have KIST.

src/or/scheduler_kist.c

@@ -16,8 +16,6 @@
 #define SCHEDULER_PRIVATE_
 #include "scheduler.h"
 
-#define TLS_PER_CELL_OVERHEAD 29
-
 #ifdef HAVE_KIST_SUPPORT
 /* Kernel interface needed for KIST. */
 #include <netinet/tcp.h>