Add Kibana application privileges to the reserved role docs

Users who create roles that are similar to the reserved roles
need to know about these.

The privileges were added to the reserved roles in
elastic/elasticsearch#40651 and elastic/elasticsearch#42757

Author: David Roberts

docs/en/stack/security/authorization/built-in-roles.asciidoc

@@ -39,11 +39,13 @@ suitable for writing beats output to {es}.
 
 [[built-in-roles-data-frame-transforms-admin]] `data_frame_transforms_admin` ::
 Grants `manage_data_frame_transforms` cluster privileges, which enable you to
-manage data frames.
+manage data frame transforms. This role also includes the `reserved_ml` {kib}
+application privilege which makes the {kib} {ml} application visible.
 
 [[built-in-roles-data-frame-transforms-user]] `data_frame_transforms_user` ::
 Grants `monitor_data_fram_transforms` cluster privileges, which enable you to
-use data frames. 
+use data frame transforms. This role also includes the `reserved_ml` {kib}
+application privilege which makes the {kib} {ml} application visible.
 
 [[built-in-roles-ingest-user]] `ingest_admin` ::
 Grants access to manage *all* index templates and *all* ingest pipeline configurations.
@@ -92,19 +94,23 @@ suitable for use within a Logstash pipeline.
 [[built-in-roles-ml-admin]] `machine_learning_admin`::
 Grants `manage_ml` cluster privileges, read access to `.ml-anomalies*`,
 `.ml-notifications*`, `.ml-state*`, `.ml-meta*` indices and write access to
-`.ml-annotations*` indices.
+`.ml-annotations*` indices. This role also includes the `reserved_ml` {kib}
+application privilege which makes the {kib} {ml} application visible.
 
 [[built-in-roles-ml-user]] `machine_learning_user`::
 Grants the minimum privileges required to view {ml} configuration,
 status, and work with results. This role grants `monitor_ml` cluster privileges,
 read access to the `.ml-notifications` and `.ml-anomalies*` indices
 (which store {ml} results), and write access to `.ml-annotations*` indices.
+This role also includes the `reserved_ml` {kib} application privilege which
+makes the {kib} {ml} application visible.
 
 [[built-in-roles-monitoring-user]] `monitoring_user`::
 Grants the minimum privileges required for any user of {monitoring} other than those
 required to use {kib}. This role grants access to the monitoring indices and grants
-privileges necessary for reading basic cluster information. Monitoring users should
-also be assigned the `kibana_user` role.
+privileges necessary for reading basic cluster information. This role also includes
+the `reserved_monitoring` {kib} application privilege which makes the {kib} monitoring
+application visible. Monitoring users should also be assigned the `kibana_user` role.
 
 [[built-in-roles-remote-monitoring-agent]] `remote_monitoring_agent`::
 Grants the minimum privileges required to write data into the monitoring indices