script: Clean-up IpcSend .sender().send() pattern (#38919)

The IpcSend trait defines a `send()` method, so doing .sender().send()
seems like it just adds a useless clone of the sender, when we could
just `send()` directly.
This only cleans up the direct usages of this pattern, there are more
instances, where a helper method is defined, which returns the
IpcSender, and the only usages also just directly call send.

Testing: No functional changes

Signed-off-by: Jonathan Schwender <schwenderjonathan@gmail.com>

components/script/dom/windowproxy.rs

@@ -356,12 +356,7 @@ impl WindowProxy {
                 dest: response.new_webview_id,
             };
 
-            document
-                .global()
-                .resource_threads()
-                .sender()
-                .send(msg)
-                .unwrap();
+            document.global().resource_threads().send(msg).unwrap();
             receiver.recv().unwrap();
         }
         Some(new_window_proxy)