Revert Output Extension

Core/RenderManager.cs

@@ -808,8 +808,8 @@ namespace ADOFAIRenderer.Core
         {
             return codec switch
             {
-                Codec.VP9 => ".webm",
+                Codec.AV1 or Codec.VP9 => ".webm",
-                Codec.AV1 or Codec.VVC => ".mkv",
+                Codec.VVC => ".mkv",
                 _ => ".mp4"
             };
         }