Fixed various page and section headings

docs/clusters/adding-clusters.md

@@ -1,4 +1,4 @@
-# Add Cluster
+# Adding clusters
 
 Add clusters by clicking the Add Cluster button in the left-side menu. You'll need to obtain a working kubeconfig for the cluster you want to add. You can either browse it from the file system or paste it as a text from the clipboard.
 

docs/clusters/removing-clusters.md

@@ -1,4 +1,4 @@
-# Remove Cluster
+# Removing clusters
 
 You can remove a Lens Clusters from your cluster list using the context-menu of the cluster item in the left-side menu. By right-clicking the cluster of choice you can hit the `Remove` button to delete it from your list.