Add to realease note DefaultDrmSessionEventListener's rename.

Its absence seems to have caused
https://github.com/google/ExoPlayer/issues/8969.

#minor-release

PiperOrigin-RevId: 375058222

RELEASENOTES.md

@@ -1036,6 +1036,7 @@ To learn more about what's new in 2.12, read the corresponding
         and the range of API levels for which they are supported is too small to
         and the range of API levels for which they are supported is too small to
         be useful.
         be useful.
     *   Remove generic types from DRM components.
     *   Remove generic types from DRM components.
+    *   Rename `DefaultDrmSessionEventListener` to `DrmSessionEventListener`.
 *   Track selection:
 *   Track selection:
     *   Add `TrackSelection.shouldCancelMediaChunkLoad` to check whether an
     *   Add `TrackSelection.shouldCancelMediaChunkLoad` to check whether an
         ongoing load should be canceled
         ongoing load should be canceled