Making extension methods from a third party library obsolete

This question is not about a method I can mark with [System.Obsolete]. The method I wanna ignore is in a dll I don't have control over.

I use a 3rd party library which contains an extension method for objects. This leads to confusion and may cause problems in the future. Is there any way to mark this extension method (or all the extension methods from a certain dll ) as obsolete externally or prevent this extension method appearing in intellisense. The problematic method is :

    public static class ExtensionMethods
    {
      public static bool IsNumeric(this object obj)
      {
        if (obj == null)
          return false;
        return obj.GetType().IsPrimitive || obj is double || (obj is Decimal || obj is DateTime) || obj is TimeSpan;
      }
    }