Use NULL for nick/blurb in GObject params

As they are only used by gstreamer for gst-inspect & other tools.
Projects like Mutter/gtk have completely dropped them as well, so follow
their path

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3505>

js/ui/workspace.js

@@ -401,11 +401,11 @@ function animateAllocation(actor, box) {
 export const WorkspaceLayout = GObject.registerClass({
     Properties: {
         'spacing': GObject.ParamSpec.double(
-            'spacing', 'Spacing', 'Spacing',
+            'spacing', null, null,
             GObject.ParamFlags.READWRITE,
             0, Infinity, 20),
         'layout-frozen': GObject.ParamSpec.boolean(
-            'layout-frozen', 'Layout frozen', 'Layout frozen',
+            'layout-frozen', null, null,
             GObject.ParamFlags.READWRITE,
             false),
     },