fix: Audio stream dispose (#1667)

* Fix audio dispose

* Missed a few

src/Discord.Net.WebSocket/Audio/Streams/RTPWriteStream.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -69,5 +69,12 @@ namespace Discord.Audio.Streams
         {
             await _next.ClearAsync(cancelToken).ConfigureAwait(false);
         }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+                _next.Dispose();
+            base.Dispose(disposing);
+        }
     }
 }