Update release notes

Author: MGaetan89

RELEASENOTES.md

@@ -6,6 +6,7 @@
     *   Add `PlaybackParameters.withPitch(float)` method for easily copying a
         `PlaybackParameters` with a new `pitch` value
         ([#2257](https://github.com/androidx/media/issues/2257)).
+    *   Deprecate `Util.SDK_INT`. Use `Build.VERSION.SDK_INT` instead.
 *   ExoPlayer:
     *   Fix sending `CmcdData` in manifest requests for DASH, HLS, and
         SmoothStreaming ([#2253](https://github.com/androidx/media/pull/2253)).