feat: Remove NGINX Service Mesh documentation

[ADubhlaoich]

Proposed changes

This commit removes the documentation for NGINX Service Mesh, which went to end of sale on July 1st 2023 and was formally archived on March 14th
2024. It removes the entire content folder for the project, as well as static example files for Grafana dashboards.

Checklist

Before sharing this pull request, I completed the following checklist:

• I read the Contributing guidelines
• My branch adheres to the Git conventions
• My content changes adhere to the F5 NGINX Documentation style guide
• If my changes involve potentially sensitive information¹, I have assessed the possible impact
• I have waited to ensure my changes pass tests, and addressed any discovered issues

Footnotes

1. Potentially sensitive information includes personally identify information (PII), authentication credentials, and live URLs. Refer to the style guide for guidance about placeholder content. ↩

[github-actions]

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[nginx-aoife]

@ADubhlaoich Can you remove this line in the linkchecker Action too so it will stop testing it.
https://github.com/nginx/documentation/blob/main/.github/workflows/linkchecker.yml#L59
Line 59 - nginx-service-mesh