fix(android): drop stray @Composable on SKELETON_PLAYLIST_ROWS const

Editing artefact from extracting LoadingCentered → SkeletonPlaylistTrackList;
the @Composable from LoadingCentered landed on the new const declaration
and Kotlin rejected it as not applicable to top-level properties.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/playlists/ui/PlaylistDetailScreen.kt

@@ -543,7 +543,6 @@ private fun TrackRow(
     }
 }
 
-@Composable
 private const val SKELETON_PLAYLIST_ROWS = 8
 
 @Composable