Remove seemingly unused code from bookmarks controller

Description

According to the original pull request for AO3-4923, the load_bookmarkable method in the bookmarks controller has an unused branch at elsif params[:chapter_id]: https://github.com/otwcode/otwarchive/blob/d27be43e444c414dc0d5620aff0df81f05c0ea7c/app/controllers/bookmarks_controller.rb#L27-L28

We'd like to remove this.

To test:

Please go to a single chapter of a multichapter work and make sure you can still create a bookmark. Then return to the chapter and make sure you can edit the bookmark.

It wouldn't hurt to try it from a chapter URL that is missing the work parameters, e.g. https://test.archiveofourown.org/chapters/####. (Note: This may or may not redirect to the full https://test.archiveofourown.org/works/####/chapters/### URL. The original pull request notes that it does redirect, but I am currently able to access that URL on staging and production without an issue.)

Environment

None

Assignee

Unassigned

Reporter

Sarken

Roadmap

Bookmarks

Priority

Low

Affects versions

Fix versions

None

Components

BackEnd

Difficulty

Easy

Required Access Level

None

Milestone

Internal 0.9
Configure