Remove Metrics from main navigation

What does this MR do and why?

Describe in detail what your merge request does and why.

Remove Metrics from main navigation

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

There is no visible change, these sections are already hidden behind the feature flag.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

There is no visible change, these sections are already hidden behind the feature flag.

• Make sure the pipeline passes
• Visit any project, there shouldn't be any errors in the console related to the navbar

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #393929 (closed)