bpf: Remove unused headers

The header <linux/version.h> is useless in sampleip_kern.c
and trace_event_kern.c, remove it.
Signed-off-by: Lu Wei <luwei32@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210324083147.149278-1-luwei32@huawei.com

samples/bpf/sampleip_kern.c

@@ -4,7 +4,6 @@
  * modify it under the terms of version 2 of the GNU General Public
  * License as published by the Free Software Foundation.
  */
-#include <linux/version.h>
 #include <linux/ptrace.h>
 #include <uapi/linux/bpf.h>
 #include <uapi/linux/bpf_perf_event.h>

samples/bpf/trace_event_kern.c

@@ -5,7 +5,6 @@
  * License as published by the Free Software Foundation.
  */
 #include <linux/ptrace.h>
-#include <linux/version.h>
 #include <uapi/linux/bpf.h>
 #include <uapi/linux/bpf_perf_event.h>
 #include <uapi/linux/perf_event.h>