[TSVB] Update copy for string indices setting popover

[jrodewig]

Summary

The TSVB data view popover includes additional copy if the Allow string indices in TSVB Kibana setting is disabled (the default). This updates the copy to better align with changes in #110253.

Testing instructions

1. In terminal, run yarn es snapshot --license=trial.
2. In a new terminal session, run yarn start.
3. Open Kibana, click Try sample data, and add the sample web logs data.
4. In the main menu, click Dashboard.
5. From the All types drop-down, select TSVB.
6. Click Panel Options. Click the gear icon in the Data view drop-down.

Checklist

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support

[elasticmachine]

Pinging @elastic/kibana-vis-editors (Team:VisEditors)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: bbd53cd
• Storybooks Preview
• Documentation Changes

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
visTypeTimeseries	486.1KB	486.1KB	+10.0B

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[gchaps]

text lgtm

[stratoula]

Code review only, LGTM!