Remove skipped from manual_playable? logic

What does this MR do and why?

Resolves #29325

Removes skipped stages from the manual button? logic to ensure the Play all button only appears for blocked stages.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Run gdk/gitpod server, login, navigate to Build > Pipelines, view one with skipped stages - there should be no play button
2. Visit http://172.16.123.1:3000/-/graphql-explorer and query for the pipeline - the action for skipped stages should be null:

{
  project(fullPath: "gitlab-org/gitlab-test") {
    pipeline(iid: 40) {
      stages {
        edges {
          node {
            id
            detailedStatus {
              id
              text
              action {
                id
                buttonTitle
              }
            }
          }
        }
      }
    }
  }
}

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