Rename AnnouncementObserver to AnnouncementListener.

I feel this wording match java naming more closely.

Bug: 68045105
Test: VTS
Change-Id: If30fa9b356b6b45fe8853bc5194c7098d0fb2aa5
diff --git a/broadcastradio/2.0/default/BroadcastRadio.h b/broadcastradio/2.0/default/BroadcastRadio.h
index 7904946..8c14d9e 100644
--- a/broadcastradio/2.0/default/BroadcastRadio.h
+++ b/broadcastradio/2.0/default/BroadcastRadio.h
@@ -36,9 +36,9 @@
     Return<void> getDabRegionConfig(getDabRegionConfig_cb _hidl_cb);
     Return<void> openSession(const sp<ITunerCallback>& callback, openSession_cb _hidl_cb) override;
     Return<void> getImage(uint32_t id, getImage_cb _hidl_cb);
-    Return<void> registerAnnouncementObserver(const hidl_vec<AnnouncementType>& enabled,
-                                              const sp<IAnnouncementObserver>& cb,
-                                              registerAnnouncementObserver_cb _hidl_cb);
+    Return<void> registerAnnouncementListener(const hidl_vec<AnnouncementType>& enabled,
+                                              const sp<IAnnouncementListener>& listener,
+                                              registerAnnouncementListener_cb _hidl_cb);
 
     std::reference_wrapper<const VirtualRadio> mVirtualRadio;
     Properties mProperties;