Remove Gitaly version in the docs

It's very hard for end user to know what version of Gitaly is running,
and they should not have to care about this detail either. Gitaly 1.21.0
was released before 11.9 was tagged, so it's an unsupported version too.

This change removes the reference.

doc/ci/merge_request_pipelines/pipelines_for_merged_results/index.md

@@ -35,10 +35,9 @@ get out of WIP status or resolve merge conflicts as soon as possible.
 
 ## Requirements and limitations
 
-Pipelines for merged results require:
+Pipelines for merged results require a [GitLab Runner][runner] 11.9 or newer.
 
-- [GitLab Runner](https://gitlab.com/gitlab-org/gitlab-runner) 11.9 or newer.
-- [Gitaly](https://gitlab.com/gitlab-org/gitaly) 1.21.0 or newer.
+[runner]: https://gitlab.com/gitlab-org/gitlab-runner
 
 In addition, pipelines for merged results have the following limitations: