Fix type issue resulting from elastic#193415 & elastic#193791 (elasti…

…c#193970)

## Summary
As the title says. Two competing changes made it in to main (elastic#193415 &
elastic#193791), causing a type issue:
https://buildkite.com/elastic/kibana-on-merge/builds/50786#019228ae-4487-45c6-867a-ba0590b1266d

cc: @davismcphee @stratoula

packages/kbn-unified-data-table/src/components/default_cell_actions.tsx

@@ -50,7 +50,7 @@ export const FilterInBtn = ({
 }) => {
   const context = useContext(UnifiedDataTableContext);
   const filteringDisabled =
-    isPlainRecord && Array.isArray(context.rows[rowIndex]?.flattened[columnId]);
+    isPlainRecord && Array.isArray(context.getRowByIndex(rowIndex)?.flattened[columnId]);
   const buttonTitle = i18n.translate('unifiedDataTable.grid.filterForAria', {
     defaultMessage: 'Filter for this {value}',
     values: { value: columnId },
@@ -85,7 +85,7 @@ export const FilterOutBtn = ({
 }) => {
   const context = useContext(UnifiedDataTableContext);
   const filteringDisabled =
-    isPlainRecord && Array.isArray(context.rows[rowIndex]?.flattened[columnId]);
+    isPlainRecord && Array.isArray(context.getRowByIndex(rowIndex)?.flattened[columnId]);
   const buttonTitle = i18n.translate('unifiedDataTable.grid.filterOutAria', {
     defaultMessage: 'Filter out this {value}',
     values: { value: columnId },