Fixes broken mapcode LSP flow from razor to c# (#10299)

Fixes #10040

Author: maryamariyan

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Endpoints/RazorCustomMessageTarget_MapCode.cs

@@ -83,8 +83,8 @@ private void ConvertCSharpFocusLocationUris(Location[][] focusLocations)
 
     private static bool SupportsMapCode(JToken token)
     {
-        return token is JObject obj
-            && obj.TryGetValue(VSInternalMethods.WorkspaceMapCodeName, out var supportsMapCode)
-            && supportsMapCode.ToObject<bool>();
+        var serverCapabilities = token.ToObject<VSInternalServerCapabilities>();
+
+        return serverCapabilities?.MapCodeProvider ?? false;
     }
 }