Change Task titles to imperative: Admin. (#4033)

_data/tasks.yml

@@ -97,7 +97,7 @@ toc:
   section:
   - docs/tasks/tls/managing-tls-in-a-cluster.md
 
-- title: Administering a Cluster
+- title: Administer a Cluster
   section:
   - docs/tasks/administer-cluster/access-cluster-api.md
   - docs/tasks/administer-cluster/access-cluster-services.md
@@ -126,7 +126,7 @@ toc:
   - docs/tasks/administer-cluster/running-cloud-controller.md
   - docs/tasks/administer-cluster/highly-available-master.md
   - docs/tasks/administer-cluster/configure-multiple-schedulers.md
-  - title: Changing Cluster Size
+  - title: Change Cluster Size
     path: https://github.com/kubernetes/kubernetes/wiki/User-FAQ#how-do-i-change-the-size-of-my-cluster/
 
 - title: Federation - Run an App on Multiple Clusters