Update unsafe JSON link (dotnet#5191)

This appears to have moved in dotnet/docs#21626.

Author: rainersigwald

xml/System.Text.Encodings.Web/JavaScriptEncoder.xml

@@ -192,7 +192,7 @@ Unlike the <xref:System.Text.Encodings.Web.JavaScriptEncoder.Default> encoding (
 
 Unlike the <xref:System.Text.Encodings.Web.JavaScriptEncoder.Default> encoder, this encoder instance allows some other characters (such as '+') to go through unescaped and therefore must be used cautiously.
 
-For more information about why this could be **unsafe**, see [Serialize all characters](/dotnet/standard/serialization/system-text-json-how-to#serialize-all-characters).
+For more information about why this could be **unsafe**, see [Serialize all characters](/dotnet/standard/serialization/system-text-json-character-encoding#serialize-all-characters).
 
           ]]></format>
         </remarks>