[8.14] Bump go-docappender to v2.1.3 (backport #13287)

[mergify]

Motivation/summary

Includes fix "Remove item.Error.Reason for unavailable_shards_exception"

backport to 8.14 for changelog. The actual 8.14 changes are included in #13286

Checklist

• Update CHANGELOG.asciidoc
• Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

Related issues

---

This is an automatic backport of pull request #13287 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of c41654f has failed:

On branch mergify/bp/8.14/pr-13287
Your branch is up to date with 'origin/8.14'.

You are currently cherry-picking commit c41654fb0.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   changelogs/8.14.asciidoc

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   NOTICE.txt
	both modified:   go.mod
	both modified:   go.sum

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally