[DOCS] Removes dashboard search batching setting (#54594)

* [DOCS] Removes dashboard search batching setting

* [DOCS] Keeps content for search setting and adds deprecation notice

* [DOCS] Fixes version notice in deprecation notice

docs/management/advanced-options.asciidoc

@@ -187,7 +187,8 @@ Refresh the page to apply the changes.
 === Search settings
 
 [horizontal]
-`courier:batchSearches`:: When disabled, dashboard panels will load individually, and search requests will terminate when
+`courier:batchSearches`:: **Deprecated in 7.6. Starting in 8.0, this setting will be optimized internally.**
+When disabled, dashboard panels will load individually, and search requests will terminate when
 users navigate away or update the query. When enabled, dashboard panels will load together when all of the data is loaded,
 and searches will not terminate.
 `courier:customRequestPreference`:: {ref}/search-request-body.html#request-body-search-preference[Request preference]