Make RemoteRendererException internal

Part of: #12221

This was part of a previous PR, but I accidentally removed it during a
rebase :(
Server/ref/Microsoft.AspNetCore.Components.Server.netcoreapp3.0.cs

Author: Ryan Nowak

src/Components/Server/ref/Microsoft.AspNetCore.Components.Server.netcoreapp3.0.cs

@@ -79,13 +79,6 @@ protected override void NavigateToCore(string uri, bool forceLoad) { }
         public static void NotifyLocationChanged(string uriAbsolute, bool isInterceptedLink) { }
     }
 }
-namespace Microsoft.AspNetCore.Components.Web.Rendering
-{
-    public partial class RemoteRendererException : System.Exception
-    {
-        public RemoteRendererException(string message) { }
-    }
-}
 namespace Microsoft.Extensions.DependencyInjection
 {
     public static partial class ComponentServiceCollectionExtensions

src/Components/Server/src/Circuits/RemoteRendererException.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Components.Web.Rendering
     /// <summary>
     /// Represents an exception related to remote rendering.
     /// </summary>
-    public class RemoteRendererException : Exception
+    internal class RemoteRendererException : Exception
     {
         /// <summary>
         /// Constructs an instance of <see cref="RemoteRendererException"/>.