[Dashboard] [Controls] Change wording of exists setting tooltip

[Heenawter]

Summary

Refer to #143762 (comment) for context.

This PR changes the wording of the exists query toggle tooltip to be more descriptive:

Checklist

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

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)

[ThomThomson]

Copy change LGTM

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 3fd1a52

Metrics [docs]

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
controls	21.9KB	22.0KB	+44.0B

Unknown metric groups

ESLint disabled in files

id	before	after	diff
osquery	1	2	+1

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	19	21	+2
fleet	58	64	+6
osquery	108	113	+5
securitySolution	440	446	+6
total			+19

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	20	22	+2
fleet	66	72	+6
osquery	109	115	+6
securitySolution	517	523	+6
total			+20

History

• 💚 Build #85615 succeeded 6bae8c5a6224db21c11de60eef71c5cdd3b318fb

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

cc @Heenawter

[KOTungseth]

LGTM!