Minor fixes in release notes

PiperOrigin-RevId: 509222489
(cherry picked from commit a90728f)

RELEASENOTES.md

@@ -81,9 +81,9 @@ This release corresponds to the
     *   Add `MediaMetadata.isBrowsable` as a replacement for
         `MediaMetadata.folderType`. The folder type will be deprecated in the
         next release.
-*   Cast extension
+*   Cast extension:
     *   Bump Cast SDK version to 21.2.0.
-*   IMA extension
+*   IMA extension:
     *   Remove player listener of the `ImaServerSideAdInsertionMediaSource` on
         the application thread to avoid threading issues.
     *   Add a property `focusSkipButtonWhenAvailable` to the
@@ -93,7 +93,7 @@ This release corresponds to the
         `ImaServerSideAdInsertionMediaSource.AdsLoader` to programmatically
         request to focus the skip button.
     *   Bump IMA SDK version to 3.29.0.
-*   Demo app
+*   Demo app:
     *   Request notification permission for download notifications at runtime
         ([#10884](https://github.com/google/ExoPlayer/issues/10884)).