Remove unused extension as it is already handled

src/LinkDotNet.Blog.Web/Features/MarkdownConverter.cs

@@ -10,7 +10,6 @@ public static class MarkdownConverter
         .UseAdvancedExtensions()
         .UseAutoIdentifiers(AutoIdentifierOptions.GitHub)
         .UseEmojiAndSmiley()
-        .UseCitations()
         .UseBootstrap()
         .Build();
 
@@ -27,4 +26,4 @@ public static string ToPlainString(string markdown)
             ? default
             : Markdown.ToPlainText(markdown, MarkdownPipeline).TrimEnd('\r', '\n');
     }
-}
+}