This reverts commit e8bfd990e44e40184249936b0bf46097660cb540.
The change:
"GNOME Shell Extension Preferences" to "GNOME Shell Extensions Preferences"
was incorrect.
A new tool, 'gnome-shell-extension-prefs' can load a new entry point from
extensions, 'prefs.js', which has an entry point to return a GTK+ widget.
This allows extensions to have their own preferences dialog, without each
extension needing to ship its own Python script and .desktop file.
https://bugzilla.gnome.org/show_bug.cgi?id=668429