Resolve "Clarify language about pipelines on Vulnerability Reports"

What does this MR do and why?

Updates text on our vulnerability report pages per #353788 (closed)

Screenshots or screen recordings

Before

After

How to set up and validate locally

1. Clone https://gitlab.com/gitlab-examples/security/security-reports or another project with vulnerabilities.
2. Verify that the Project, Group and Instance level Vulnerability reports display the updated text
3. Verify that the Learn more link now points to the vulnerability report documentation (previously the security dashboard) (deferred to a separate issue)

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 #353788 (closed)