Add Gitaly to the list of projects using documentation tests

doc/development/documentation/testing.md

@@ -25,8 +25,11 @@ in the relevant projects:
 - <https://gitlab.com/gitlab-org/charts/gitlab/-/blob/master/.gitlab-ci.yml>
 - <https://gitlab.com/gitlab-org/cloud-native/gitlab-operator/-/blob/master/.gitlab-ci.yml>
 
-We also run some documentation tests in the GitLab Development Kit project:
-<https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/.gitlab/ci/test.gitlab-ci.yml>.
+We also run some documentation tests in the:
+
+- GitLab Development Kit project:
+  <https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/.gitlab/ci/test.gitlab-ci.yml>.
+- Gitaly project: <https://gitlab.com/gitlab-org/gitaly/-/blob/master/.gitlab-ci.yml>.
 
 ## Run tests locally