feat: make most_played_track_uri optional in ArtistListener struct

crates/analytics/src/types/artist.rs

···
     pub avatar: String,
     pub total_artist_plays: i64,
     pub most_played_track: String,
-    pub most_played_track_uri: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub most_played_track_uri: Option<String>,
     pub track_play_count: i64,
 }