[8.1] [BUG] Adding .internal indices permission necessity for rule pr…

…eview feature permission docs (backport #3067) (#3102)

Co-authored-by: Nastasha Solomon <79124755+nastasha-solomon@users.noreply.github.com>

docs/detections/rules-ui-create.asciidoc

@@ -256,7 +256,7 @@ field values.
 
 You can preview custom query, threshold, machine learning, or event correlation rules to learn how noisy a rule will be before submitting it. If necessary, you can then adjust the rule's query.
 
-NOTE: To preview rules, you need the `read` privilege to the `.preview.alerts-security.alerts-<space-id>` index and `All` privileges for the Security feature. Refer to <<detections-permissions-section>> for more information.
+NOTE: To preview rules, you need the `read` privilege for the `.preview.alerts-security.alerts-<space-id>` and `.internal.preview.alerts-security.alerts-<space-id>-*` indices, plus `All` privileges for the Security feature. Refer to <<detections-permissions-section>> for more information.
 
 To preview a rule:
 

docs/getting-started/detections-req.asciidoc

@@ -85,7 +85,11 @@ a|The `manage`, `write`,`read`, and `view_index_metadata` index privileges for t
 
 | Preview rules
 |N/A
-a| The `read` privilege for the `.preview.alerts-security.alerts-<space-id>` index
+a| The `read` privilege for the following indices:
+
+* `.preview.alerts-security.alerts-<space-id>`
+* `.internal.preview.alerts-security.alerts-<space-id>-*`
+
 |{kib} space `All` privileges for the `Security` feature (refer to
 {kibana-ref}/xpack-spaces.html#spaces-control-user-access[Feature access based on user privileges])