sync_timing.py: remove unnecessary header file

<linux/blkdev.h> is not needed.
Signed-off-by: Liu Bo <liub.liubo@gmail.com>

examples/tracing/sync_timing.py

@@ -14,7 +14,6 @@ from bcc import BPF
 # load BPF program
 b = BPF(text="""
 #include <uapi/linux/ptrace.h>
-#include <linux/blkdev.h>
 
 BPF_HASH(last);