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/Android.bp b/broadcastradio/2.0/Android.bp
index 7409005..2434fdc 100644
--- a/broadcastradio/2.0/Android.bp
+++ b/broadcastradio/2.0/Android.bp
@@ -8,7 +8,7 @@
     },
     srcs: [
         "types.hal",
-        "IAnnouncementObserver.hal",
+        "IAnnouncementListener.hal",
         "IBroadcastRadio.hal",
         "ICloseHandle.hal",
         "ITunerCallback.hal",