Fix link to volume label support in changelog

Signed-off-by: Martin Honermeyer <maze@strahlungsfrei.de>
(cherry picked from commit bb06e138e47ff2a7b1b3553a6337a2bb64b58907)
Signed-off-by: Victor Vieux <vieux@docker.com>

CHANGELOG.md

@@ -179,7 +179,7 @@ be found.
 
 ### Volume
 
-+ Add support for labels on volumes [#25628](https://github.com/docker/docker/pull/21567)
++ Add support for labels on volumes [#21270](https://github.com/docker/docker/pull/21270)
 + Add support for filtering volumes by label [#25628](https://github.com/docker/docker/pull/25628)
 * Add a `--force` flag in `docker volume rm` to forcefully purge the data of the volume that has already been deleted [#23436](https://github.com/docker/docker/pull/23436)
 * Enhance `docker volume inspect` to show all options used when creating the volume [#26671](https://github.com/docker/docker/pull/26671)