Update release notes for Media3 1.6.0-alpha03 release

PiperOrigin-RevId: 723512116
(cherry picked from commit 6a4aa45)

Author: rohitjoins

RELEASENOTES.md

@@ -1,17 +1,17 @@
 # Release notes
 
-### Unreleased changes
+## 1.6
+
+### 1.6.0-alpha03 (2025-02-06)
+
+This release includes the following changes since the
+[1.6.0-alpha02 release](#160-alpha02-2025-01-30):
 
-*   Common Library:
 *   ExoPlayer:
     *   Add option to `ClippingMediaSource` to allow clipping in unseekable
         media.
     *   Fix bug where seeking with pre-warming could block following media item
         transition.
-*   Transformer:
-*   Track Selection:
-*   Extractors:
-*   DataSource:
 *   Audio:
     *   Make `androidx.media3.common.audio.SonicAudioProcessor` final.
 *   Video:
@@ -22,36 +22,11 @@
     *   Add experimental `ExoPlayer` AV1 sample dependency parsing to speed up
         seeking. Enable it with the new
         `DefaultRenderersFactory.experimentalSetParseAv1SampleDependencies` API.
-*   Text:
-*   Metadata:
-*   Image:
-*   DataSource:
-*   DRM:
-*   Effect:
 *   Muxers:
     *   Disable `Mp4Muxer` sample batching and copying by default.
-*   IMA extension:
-*   Session:
-*   UI:
-*   Downloads:
-*   OkHttp Extension:
-*   Cronet Extension:
-*   RTMP Extension:
-*   HLS Extension:
-*   DASH Extension:
-*   Smooth Streaming Extension:
-*   RTSP Extension:
-*   Decoder Extensions (FFmpeg, VP9, AV1, etc.):
-*   MIDI extension:
-*   Leanback extension:
-*   Cast Extension:
-*   Test Utilities:
-*   Demo app:
 *   Remove deprecated symbols:
     *   Removed `androidx.media3.exoplayer.audio.SonicAudioProcessor`.
 
-## 1.6
-
 ### 1.6.0-alpha02 (2025-01-30)
 
 This release includes the following changes since the