[Discover] Update docs to remove discover:showLegacyFieldTopValues (#…

…197981)

## Summary

This PR updates docs as a followup for
#155503

### Checklist

- [x]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials

Co-authored-by: Davis McPhee <[email protected]>
(cherry picked from commit 75195b4)

docs/management/advanced-options.asciidoc

@@ -330,9 +330,6 @@ the minimum and maximum values of a numeric field or a map of a geo field.
 [[discover:showMultiFields]]`discover:showMultiFields`::
 Controls the display of multi-fields in the expanded document view.
 
-[[discover:showLegacyFieldTopValues]]`discover:showLegacyFieldTopValues`::
-To calculate the top values for a field in the sidebar using 500 instead of 5,000 records per shard, turn on this option.
-
 [[discover-sort-defaultorder]]`discover:sort:defaultOrder`::
 The default sort direction for time-based data views.
 

packages/kbn-management/settings/setting_ids/index.ts

@@ -83,7 +83,6 @@ export const DISCOVER_SAMPLE_SIZE_ID = 'discover:sampleSize';
 export const DISCOVER_SEARCH_FIELDS_FROM_SOURCE_ID = 'discover:searchFieldsFromSource';
 export const DISCOVER_SEARCH_ON_PAGE_LOAD_ID = 'discover:searchOnPageLoad';
 export const DISCOVER_SHOW_FIELD_STATISTICS_ID = 'discover:showFieldStatistics';
-export const DISCOVER_SHOW_LEGACY_FIELD_TOP_VALUES_ID = 'discover:showLegacyFieldTopValues';
 export const DISCOVER_SHOW_MULTI_FIELDS_ID = 'discover:showMultiFields';
 export const DISCOVER_SORT_DEFAULT_ORDER_ID = 'discover:sort:defaultOrder';
 export const DOC_TABLE_HIDE_TIME_COLUMNS_ID = 'doc_table:hideTimeColumn';