chore: remove obsolete comments from OpenApiDocumentProvider (#63776)

Author: xC0dex

src/OpenApi/src/Services/OpenApiDocumentProvider.cs

@@ -47,9 +47,6 @@ public async Task GenerateAsync(string documentName, TextWriter writer, OpenApiS
         // See OpenApiServiceCollectionExtensions.cs for more info.
         var lowercasedDocumentName = documentName.ToLowerInvariant();
 
-        // Microsoft.OpenAPI does not provide async APIs for writing the JSON
-        // document to a file. See https://github.com/microsoft/OpenAPI.NET/issues/421 for
-        // more info.
         var targetDocumentService = serviceProvider.GetRequiredKeyedService<OpenApiDocumentService>(lowercasedDocumentName);
         using var scopedService = serviceProvider.CreateScope();
         var document = await targetDocumentService.GetOpenApiDocumentAsync(scopedService.ServiceProvider);