Updated Elasticsearch install docs link to point to 6.8 vs "current" as the...

Updated Elasticsearch install docs link to point to 6.8 vs "current" as the current version is 7.3  (which isn't supported by gitlab). Also added a link to Elastic Cloud as an alternative option to AWS Elasticsearch Service.

doc/integration/elasticsearch.md

@@ -25,17 +25,16 @@ special searches:
 ## Installing Elasticsearch
 
 Elasticsearch is _not_ included in the Omnibus packages. You will have to
-[install it yourself](https://www.elastic.co/guide/en/elasticsearch/reference/current/install-elasticsearch.html "Elasticsearch installation documentation")
+[install it yourself](https://www.elastic.co/guide/en/elasticsearch/reference/6.8/install-elasticsearch.html "Elasticsearch 6.8 installation documentation")
 whether you are using the Omnibus package or installed GitLab from source.
 Providing detailed information on installing Elasticsearch is out of the scope
 of this document.
 
 NOTE: **Note:**
 Elasticsearch should be installed on a separate server, whether you install
-it yourself or by using the
-[Amazon Elasticsearch](https://docs.aws.amazon.com/elasticsearch-service/latest/developerguide/es-gsg.html)
-service. Running Elasticsearch on the same server as GitLab is not recommended
-and it will likely cause performance degradation on the GitLab installation.
+it yourself or use a cloud hosted offering like Elastic's [Elasticsearch Service](https://www.elastic.co/products/elasticsearch/service) (available on AWS, GCP, or Azure) or the
+[Amazon Elasticsearch](http://docs.aws.amazon.com/elasticsearch-service/latest/developerguide/es-gsg.html) service. Running Elasticsearch on the same server as GitLab is not recommended
+and will likely cause a degradation in GitLab instance performance.
 
 NOTE: **Note:**
 **For a single node Elasticsearch cluster the functional cluster health status will be yellow** (will never be green) because the primary shard is allocated but replicas can not be as there is no other node to which Elasticsearch can assign a replica.