fix: remove persistence nullability

Author: VisualBean

src/LEGO.AsyncAPI.Bindings/Pulsar/PulsarChannelBinding.cs

@@ -19,7 +19,7 @@ public class PulsarChannelBinding : ChannelBinding<PulsarChannelBinding>
         /// <summary>
         /// persistence of the topic in Pulsar persistent or non-persistent.
         /// </summary>
-        public Persistence? Persistence { get; set; }
+        public Persistence Persistence { get; set; }
 
         /// <summary>
         /// Topic compaction threshold given in bytes.