docs: Add note to Helm values file (#15637)

Author: JStickler

docs/sources/setup/install/helm/reference.md

@@ -9483,6 +9483,21 @@ false
 			<td><pre lang="json">
 {}
 </pre>
+</td>
+		</tr>
+		<tr>
+			<td>read.persistence</td>
+			<td>object</td>
+			<td>read.persistence is used only if legacyReadTarget is set to true</td>
+			<td><pre lang="json">
+{
+  "annotations": {},
+  "enableStatefulSetAutoDeletePVC": true,
+  "selector": null,
+  "size": "10Gi",
+  "storageClass": null
+}
+</pre>
 </td>
 		</tr>
 		<tr>

production/helm/loki/values.yaml

@@ -1577,6 +1577,7 @@ read:
   tolerations: []
   # -- The default is to deploy all pods in parallel.
   podManagementPolicy: "Parallel"
+  # -- read.persistence is used only if legacyReadTarget is set to true
   persistence:
     # -- Enable StatefulSetAutoDeletePVC feature
     enableStatefulSetAutoDeletePVC: true