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/idbobjectstore.rs

@@ -128,7 +128,6 @@ impl IDBObjectStore {
 
         self.global()
             .resource_threads()
-            .sender()
             .send(IndexedDBThreadMsg::Sync(operation))
             .unwrap();