fix: remove dead API doc links to internal scene event types (UUM-131558)

The NetworkSceneManager class summary and SceneEventDelegate XML docs
referenced the internal types SceneEventMessage and SceneEventData via
<see cref>, which generate hyperlinks in the DocFX-generated API docs.
Because those types are internal they have no public documentation
pages, so the links resolved to missing pages.

Convert the descriptive class-summary references to inline code (<c>)
and drop the internal SceneEventData entry from the SceneEventDelegate
'See also' list (a user cannot reference an internal type), keeping the
public SceneEvent link.

Author: michalChrobot

com.unity.netcode.gameobjects/Runtime/SceneManagement/NetworkSceneManager.cs

@@ -143,7 +143,7 @@ public class SceneEvent
 
     /// <summary>
     /// Main class for managing network scenes when <see cref="NetworkConfig.EnableSceneManagement"/> is enabled.
-    /// Uses the <see cref="SceneEventMessage"/> message to communicate <see cref="SceneEventData"/> between the server and client(s)
+    /// Uses the <c>SceneEventMessage</c> message to communicate <c>SceneEventData</c> between the server and client(s)
     /// </summary>
     [Serializable]
     public class NetworkSceneManager : IDisposable
@@ -162,8 +162,7 @@ public class NetworkSceneManager : IDisposable
         /// <summary>
         /// The delegate callback definition for scene event notifications.<br />
         /// See also: <br />
-        /// <see cref="SceneEvent"/><br />
-        /// <see cref="SceneEventData"/>
+        /// <see cref="SceneEvent"/>
         /// </summary>
         /// <param name="sceneEvent">SceneEvent which contains information about the scene event, including type, progress, and scene details</param>
         public delegate void SceneEventDelegate(SceneEvent sceneEvent);