[Lens] Restore TSDB downsample tests (elastic#164410)

## Summary

Fixes elastic#163971 finally.

This PR keep tracks of ES fix for the TSDB downsampling and will be
ready to restore the tests once the bug has been fixed.

The issue has been fixed with
elastic/elasticsearch#98840 on ES side.

### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

(cherry picked from commit 3aa9d7b)

x-pack/test/functional/apps/lens/group4/tsdb.ts

@@ -384,8 +384,7 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
         });
       });
 
-      // FAILING ES PROMOTION: https://github.com/elastic/kibana/issues/163971
-      describe.skip('for rolled up metric (downsampled)', () => {
+      describe('for rolled up metric (downsampled)', () => {
         it('defaults to average for rolled up metric', async () => {
           await PageObjects.lens.switchDataPanelIndexPattern(downsampleDataView.dataView);
           await PageObjects.lens.removeLayer();
@@ -622,21 +621,21 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
             { index: 'regular_index', create: true, removeTSDBFields: true },
           ],
         },
-        // {
-        //   name: 'Dataview with an additional downsampled TSDB stream',
-        //   indexes: [
-        //     { index: initialIndex },
-        //     { index: 'tsdb_index_2', create: true, tsdb: true, downsample: true },
-        //   ],
-        // },
-        // {
-        //   name: 'Dataview with additional regular index and a downsampled TSDB stream',
-        //   indexes: [
-        //     { index: initialIndex },
-        //     { index: 'regular_index', create: true, removeTSDBFields: true },
-        //     { index: 'tsdb_index_2', create: true, tsdb: true, downsample: true },
-        //   ],
-        // },
+        {
+          name: 'Dataview with an additional downsampled TSDB stream',
+          indexes: [
+            { index: initialIndex },
+            { index: 'tsdb_index_2', create: true, tsdb: true, downsample: true },
+          ],
+        },
+        {
+          name: 'Dataview with additional regular index and a downsampled TSDB stream',
+          indexes: [
+            { index: initialIndex },
+            { index: 'regular_index', create: true, removeTSDBFields: true },
+            { index: 'tsdb_index_2', create: true, tsdb: true, downsample: true },
+          ],
+        },
         {
           name: 'Dataview with an additional TSDB stream',
           indexes: [{ index: initialIndex }, { index: 'tsdb_index_2', create: true, tsdb: true }],