Fix typo in in_tail doc

[dukex]

Hi guys, just fixing a small typo in in_tail doc.

[fujimotos]

Thanks! Can you sign your commit and push again?

As a policy, we require each commit to be signed by the author. We cannot merge one lacking a signoff line.

Here is how to sign your commit:

$ git commit --amend -s
$ git push -f

[dukex]

Sorry @fujimotos, now I believe it's ok, Thanks

[fujimotos]

Thanks!