fix(regression): GTK refactor causing updates to be missed

Regression introduced by recent GTK refactor.

The `glib_recv` macros  previously using the passed in expression as the receiver, which was causing a new receiver to be created *every* time an event was received. This caused some peculiar behaviours where some events just never got through if sent too close to each other.

This was most obvious in the `workspaces` module.

Fixes #381

src/style.rs

@@ -35,7 +35,7 @@ pub fn load_css(style_path: PathBuf) {
         GTK_STYLE_PROVIDER_PRIORITY_USER as u32,
     );
 
-    let (tx, mut rx) = mpsc::channel(8);
+    let (tx, rx) = mpsc::channel(8);
 
     spawn(async move {
         let style_path2 = style_path.clone();