[DOCS] Removes out-dated X-Pack content

Author: lcawl

docs/upgrading-stack.asciidoc

@@ -16,8 +16,9 @@ We recommend upgrading to the most recent 5.6 before upgrading to {version}. {xp
 provides a free Upgrade Assistant that identifies issues you need to address
 before upgrading and simplifies migrating indices that need to be reindexed
 before you upgrade. The Upgrade Assistant is enabled with both Trial and
-Basic licenses. You can install X-Pack solely for the purpose of upgrading.
-There's no obligation to continue using X-Pack once your upgrade is complete.
+Basic licenses. You can install {xpack} solely for the purpose of upgrading. In 
+6.3 and later, {xpack} is automatically installed when you install {es}, {kib}, 
+and Logstash. 
 
 Rolling upgrades are supported when upgrading from Elasticsearch 5.6 to
 {version}, a full cluster restart is not always required. Upgrading from any
@@ -49,7 +50,6 @@ and make the necessary changes so your code is compatible with {version}:
 ** {hadoop-ref}/breaking-changes.html[Elasticsearch Hadoop {version} breaking changes]
 ** {kibana-ref}/breaking-changes.html[Kibana {version} breaking changes]
 ** {logstash-ref}/breaking-changes.html[Logstash {version} breaking changes]
-** {xpack-ref}/xpack-breaking-changes.html[{xpack} {version} breaking changes]
 
 [IMPORTANT]
 ===============================
@@ -76,7 +76,7 @@ internal indices after you install Elasticsearch {version}.
 . If you use {xpack} to secure your cluster:
 .. Make sure TLS is enabled to encrypt communications between nodes. TLS must
 be enabled to upgrade to {version}. For more information, see
-{xpack-ref}/encrypting-communications.html[Encrypting Communications].
+{stack-ov}/encrypting-communications.html[Encrypting communications].
 +
 NOTE: Enabling TLS requires a full cluster restart. Nodes that have TLS
 enabled cannot communicate with nodes that do not have TLS enabled. You must
@@ -85,11 +85,11 @@ restart all nodes to maintain communication across the cluster.
 .. Make sure real passwords are configured for the built-in `elasticsearch`,
 `kibana`, and `logstash_system` users. They cannot use the 5.x default
 password (`changeme`). For more information, see
-{xpack-ref}/setting-up-authentication.html[Setting Up User Authentication].
+{stack-ov}/built-in-users.html[Built-in users].
 
 . Stop any {xpack} machine learning jobs that are running before starting the
 upgrade process. See
-{xpack-ref}/stopping-ml.html[Stopping Machine Learning].
+{stack-ov}/stopping-ml.html[Stopping machine learning].
 
 IMPORTANT: Test upgrades in a dev environment before upgrading your
 production cluster.
@@ -100,15 +100,10 @@ production cluster.
 
 Upgrade the Elastic Stack products you use in the following order:
 
-// TODO: Add link to x-pack upgrade doc
-
 . Elasticsearch Hadoop: {hadoop-ref}/install.html[install instructions]
 . Elasticsearch: {ref}/setup-upgrade.html[upgrade instructions]
-. {xpack} for Elasticsearch
 . Kibana: {kibana-ref}/upgrade.html[upgrade instructions]
-. {xpack} for Kibana
 . Logstash: {logstash-ref}/upgrading-logstash.html[upgrade instructions]
-. {xpack} for Logstash
 . Beats: {beats-ref}/upgrading.html[upgrade instructions]
 
 NOTE: Logstash 6.0+ and Beats 6.0+ are compatible with all 6.x versions of
@@ -184,7 +179,7 @@ but it requires a {ref}/restart-upgrade.html[full cluster restart] and you must
 manually reindex any 2.x indices you need to carry forward to {major-version}.
 
 IMPORTANT: If you use Kibana or {xpack}, you also need to upgrade the
-internal Kibana and X-Pack indices. For information about upgrading them
+internal Kibana and {xpack} indices. For information about upgrading them
 after you install Elasticsearch {version}, see
 <<upgrade-internal-indices, Upgrading internal indices>>.
 
@@ -236,7 +231,7 @@ You can use your regular administration credentials to upgrade the other
 internal indices using the `_xpack/migration/upgrade` API.
 
 TIP: Once you upgrade the `.kibana` index, you can run Kibana and use the
-X-Pack Reindex Helper UI to upgrade the other indices.
+{xpack} Reindex Helper UI to upgrade the other indices.
 
 [[upgrade-elastic-stack-for-elastic-cloud]]
 === Upgrading on Elastic Cloud