cleanup: Use deepUnpack() intead of deep_unpack()

deep_unpack() is just a backwards compability alias for deepUnpack()[1].
The new name makes it more clear that this is not a C function, start to
use it.

[1] 13e662a29d

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2416>

tests/interactive/gapplication.js

@@ -13,7 +13,7 @@ function do_action_param(action, parameter) {
 }
 
 function do_action_toggle(action) {
-    action.set_state(GLib.Variant.new('b', !action.state.deep_unpack()));
+    action.set_state(GLib.Variant.new('b', !action.state.deepUnpack()));
     print ("Toggled");
 }