fix: use valid version for fleet-server-7.16

[mdelapenya]

The backport updated the version to 8.1, which is incorrect

What does this PR do?

Uses 7.16 version for fleet-server

Why is it important?

The current value was added by a backport, so it's wrong

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 run the Unit tests (make unit-test), and they are passing locally
• I have run the End-2-End tests for the suite I'm working on, and they are passing locally
• I have noticed new Go dependencies (run make notice in the proper directory)

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Caused by [7.16](backport #2064) fix: update stack deployment to follow Users&Roles best practices #2103

[juliaElastic]

🚀

[elasticmachine]

💚 Flaky test report

Tests succeeded.

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.