Drop obsolete customization to hide the "Tor" section in preferences

32a2cf0fc9dc3c9e00d93be816ae5013f66b4468 should not be necessary anymore with Tor Browser 9.0.1 and newer: https://trac.torproject.org/projects/tor/ticket/32210.

Feature Branch: bugfix/17143-17214-12023-remove-obsolete-tor-browser-customization+force-all-tests

Original created by @intrigeri on 17214 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information