samples/bpf: Fix double word in comments

Remove the repeated word "by" in comments.

Signed-off-by: Shaomin Deng <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Martin KaFai Lau <[e-mail]>

samples/bpf/hbm_edt_kern.c

···
  *
  * If the credit is below the drop threshold, the packet is dropped. If it
  * is a TCP packet, then it also calls tcp_cwr since packets dropped by
- * by a cgroup skb BPF program do not automatically trigger a call to
+ * a cgroup skb BPF program do not automatically trigger a call to
  * tcp_cwr in the current kernel code.
  *
  * This BPF program actually uses 2 drop thresholds, one threshold