Silence new zvariant De/SerializeDict deprecations

Questionable exercise converting to serde with much more boilerplate, and
breaking compat with older zvariant versions. Plus maybe this will be
undeprecated back.

src/dbus/gnome_shell_introspect.rs

@@ -1,3 +1,5 @@
+#![allow(deprecated)] // Maybe De/SerializeDict will be undeprecated in the future.
+
 use std::collections::HashMap;
 
 use zbus::fdo::{self, RequestNameFlags};

src/dbus/mutter_screen_cast.rs

@@ -1,3 +1,5 @@
+#![allow(deprecated)] // Maybe De/SerializeDict will be undeprecated in the future.
+
 use std::collections::HashMap;
 use std::mem;
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};