[Manual backport][Heartbeat] Fix hint generator test

[emilioalvap]

What does this PR do?

Manual backport of hint autodiscovery tests flakiness here: #34307

Why is it important?

With #34759, same test flakiness (which was fixed later on 8.X) has been introduced into 7.17, this manual backport addresses that.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

[elasticmachine]

Pinging @elastic/uptime (Team:Uptime)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2023-03-10T15:32:07.873+0000

• Duration: 45 min 27 sec

Test stats 🧪

Test	Results
Failed	0
Passed	1195
Skipped	13
Total	1208

💚 Flaky test report

Tests succeeded.

🤖 GitHub comments

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[andrewvc]

LGTM