[TSVB] Unskips the rollup test (elastic#169620)

## Summary

I unskipped this test and run the tests 100 times
https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/3692#

The failure doesn't seem to happen so I think we can unskip it.

Closes elastic#168267

x-pack/test/functional/apps/rollup_job/tsvb.js

@@ -24,8 +24,7 @@ export default function ({ getService, getPageObjects }) {
   const fromTime = 'Oct 15, 2019 @ 00:00:01.000';
   const toTime = 'Oct 15, 2019 @ 19:31:44.000';
 
-  // FLAKY: https://github.com/elastic/kibana/issues/168267
-  describe.skip('tsvb integration', function () {
+  describe('tsvb integration', function () {
     //Since rollups can only be created once with the same name (even if you delete it),
     //we add the Date.now() to avoid name collision if you run the tests locally back to back.
     const rollupJobName = `tsvb-test-rollup-job-${Date.now()}`;