bpf: Fix comment for helper bpf_current_task_under_cgroup()

Fix the descriptions of the return values of helper bpf_current_task_under_cgroup().

Fixes: c6b5fb8690fa ("bpf: add documentation for eBPF helpers (42-50)")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220310155335.1278783-1-hengqi.chen@gmail.com

include/uapi/linux/bpf.h

@@ -2302,8 +2302,8 @@ union bpf_attr {
  * 	Return
  * 		The return value depends on the result of the test, and can be:
  *
- *		* 0, if current task belongs to the cgroup2.
- *		* 1, if current task does not belong to the cgroup2.
+ *		* 1, if current task belongs to the cgroup2.
+ *		* 0, if current task does not belong to the cgroup2.
  * 		* A negative error code, if an error occurred.
  *
  * long bpf_skb_change_tail(struct sk_buff *skb, u32 len, u64 flags)