Remove unused partial

What does this MR do and why?

This removes an apparently unused partial.

The last reference to this partial appears to have been removed exactly three years ago(!) by gitlab-foss!22196 (merged).

Nowadays its functionality appears to be implemented by ~/repository/components/breadcrumbs.vue.

Screenshots or screen recordings

n/a

How to set up and validate locally

• Does the pipeline pass?
• Do any project pages look broken?

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.