Pipeline status badge missing "manual"

What does this MR do and why?

Adding "manual" as a pipeline status badge in the documentation.

Screenshots or screen recordings

How to set up and validate locally

1. Navigate to https://docs.gitlab.com/ee/ci/pipelines/settings.html#pipeline-status-badge and ensure "manual" is an option under the Pipeline status badge header.

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 #362371 (closed)