[Monitoring] Fix system index label in Stack Monitoring screen (elast…

…ic#194839)

Closes elastic#194838

## Summary

This PR wraps up the change made in
elastic#76946 (issue
elastic#77492)

The change was about relabeling the "Show system indices" toggle showing
below to "Filter for system indices", but when no indices show up, the
warning message still contains the old text, i.e. "Show system indices"


![Image](https://github.com/user-attachments/assets/9c3003a8-5689-4d3a-8175-8e707d1ec40a)


![Image](https://github.com/user-attachments/assets/cfdd9ba1-d87d-47ae-afb9-4fa81473230d)

### Checklist

- [X] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)
- [X] This renders correctly on smaller devices using a responsive
layout. (You can test this [in your
browser](https://www.browserstack.com/guide/responsive-testing-on-local-server))
- [X] This was checked for [cross-browser
compatibility](https://www.elastic.co/support/matrix#matrix_browsers)

x-pack/plugins/monitoring/public/components/elasticsearch/indices/indices.js

@@ -138,7 +138,7 @@ const getNoDataMessage = () => {
       <p>
         <FormattedMessage
           id="xpack.monitoring.elasticsearch.indices.howToShowSystemIndicesDescription"
-          defaultMessage="If you are looking for system indices (e.g., .kibana), try checking &lsquo;Show system indices&rsquo;."
+          defaultMessage="If you are looking for system indices (e.g., .kibana), try checking &lsquo;Filter for system indices&rsquo;."
         />
       </p>
     </div>