aws: Ensure task stopping on paused-to-ready state change

Disconnect channel so that srcpad task can stop immediately

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/2440>

net/aws/src/transcriber2/imp.rs

@@ -1186,6 +1186,7 @@ impl ElementImpl for Transcriber {
                 })?;
             }
             gst::StateChange::PausedToReady => {
+                let _ = self.state.lock().unwrap().result_rx.take();
                 self.disconnect(true);
             }
             _ => (),

net/aws/src/translate/imp.rs

@@ -1245,6 +1245,7 @@ impl ElementImpl for Translate {
                 })?;
             }
             gst::StateChange::PausedToReady => {
+                let _ = self.state.lock().unwrap().translate_tx.take();
                 self.disconnect(true);
             }
             _ => (),