Update to zbus 5.x

https://github.com/dbus2/zbus/releases/tag/zbus-5.0.0

Now requires `pub` on uses of `#[proxy]` if the generated types should
be `pub`.

switcheroo-control/src/lib.rs

@@ -31,7 +31,7 @@ use zbus::{
 	default_service = "net.hadess.SwitcherooControl",
 	default_path = "/net/hadess/SwitcherooControl"
 )]
-trait SwitcherooControl {
+pub trait SwitcherooControl {
 	/// GPUs property
 	#[zbus(property, name = "GPUs")]
 	fn gpus(