Clean up unused header app init code

What does this MR do and why?

This MR removes initiation code for blob controls and ref selector app for tree/blob page. Both apps are now part of the header app (ref and ref). All initiations were previously used in app/views/projects/tree/_tree_header.html.haml. This partial has been removed as part of the clean up for header app feature flag !193201 (diffs).

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

Visit a file in a repository, blob controls (e.g. find file, blame) should work as before.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.