Use file icons from GitLab UI

What does this MR do and why?

This let's us update the file icons more easily with a proper SVG release process.

See: https://gitlab.com/gitlab-org/gitlab-svgs/-/issues/97

Another benefit: The new file is 218KB instead of 400KB while covering the same icons.

Screenshots or screen recordings

Before	After

How to set up and validate locally

Look at any repo file view. Might need to restart rails-web after switching branches.

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.