[TSVB] Fix flaky test (#154519)

## Summary

Closes #154372

Runner 100 times
https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/2094

I dont think that this test is super flaky. I just added the waiting
after clicking the seriesOption as I guess it might make it even more
stable

x-pack/test/functional/apps/lens/open_in_lens/tsvb/table.ts

@@ -88,6 +88,7 @@ export default function ({ getPageObjects, getService }: FtrProviderContext) {
       await visualBuilder.setStaticValue(10);
       await header.waitUntilLoadingHasFinished();
       await visualBuilder.clickSeriesOption();
+      await header.waitUntilLoadingHasFinished();
       await visualBuilder.setFieldForAggregateBy('bytes');
       await visualBuilder.setFunctionForAggregateFunction('Sum');
       await header.waitUntilLoadingHasFinished();