Public share of a PDF file with download set to "hidden" does not open automatically

[elzody]

Describe the bug
When sharing a PDF via a public share link, it will not automatically open if the download button is set to be hidden. When this option is unchecked (download button will be shown), the PDF is displayed just fine, however.

To Reproduce
Steps to reproduce the behavior:

1. Go to any PDF on your instance
2. Create a public share with "hide download" checked
3. Open the public share
4. The PDF will not be displayed

Expected behavior
The PDF will be displayed regardless, because there is no point in not showing it and also not being able to download it.

Details
The issue began on stable27 after I introduced #3600. Also, files.js seems to be legacy code and not needed, which I think caused the issue, since it was being loaded in addition to the public-share-handling public.js I introduced