Use valid path when loading the org.gnome.nm-applet.eap schema

Since glib 2.39, GSettings verifies the path validity [0].
A valid path begins and ends with '/' and does not contain two
consecutive '/'. We were missing the trailing '/', leading to an assert
when trying to load the org.gnome.nm-applet.eap schema.

[0] https://git.gnome.org/browse/glib/commit/?id=6568843624e9f46a3c51cd8c1a6670896a48f1fb