Missing top border in file component

Summary

The top border for the file viewer/editor is missing in a lot of places, e.g. new snippets or new files.

Possible fixes

This is due to .file-holder having border-top: 0 defined, which might have been introduced to avoid a double border after adding border-top: 1px solid #e5e5e5 to .file-title-flex-parent, which is located right underneath .file-holder.