[DOCS] Edit licensing API summaries (#3284)

(cherry picked from commit 1125814)

Author: lcawl

docs/overlays/elasticsearch-shared-overlays.yaml

@@ -113,6 +113,9 @@ actions:
         - name: license
           x-displayName: Licensing
           description: Licensing APIs enable you to manage your licenses.
+          externalDocs:
+            url: https://www.elastic.co/subscriptions
+            description: For more information about the different types of licenses, refer to Elastic subscriptions
         - name: logstash
           x-displayName: Logstash
           description: >