[Data source] Fix datasource filtering issue (#5484)

Fixes data source filtering issue within Discover. When typing into the index pattern
field it will filter out and highlight the value being typed.

Issue resolved:
#5533
#5499
#5468
#5319

Signed-off-by: Eric <menwe@amazon.com>
(cherry picked from commit dadfefa)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

src/plugins/data/public/data_sources/datasource_selector/datasource_selectable.tsx

@@ -129,7 +129,6 @@ export const DataSourceSelectable = ({
       onChange={handleSourceChange}
       singleSelection={singleSelection}
       isClearable={false}
-      async
     />
   );
 };