Fix typo in doc/api/group_clusters.md

doc/api/group_clusters.md

@@ -8,7 +8,7 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/30213) in GitLab 12.1.
 
-Similar to [project-level](../user/project/clusters/index.md) and
+Similarly to [project-level](../user/project/clusters/index.md) and
 [instance-level](../user/instance/clusters/index.md) Kubernetes clusters,
 group-level Kubernetes clusters allow you to connect a Kubernetes cluster to
 your group, enabling you to use the same cluster across multiple projects.