Fix exsl link (#8925)

Author: gewarren

xml/System.Xml.Xsl.Runtime/XsltFunctions.xml

@@ -120,7 +120,7 @@
       </Parameters>
       <Docs>
         <param name="value">The <see cref="T:System.Xml.XPath.XPathItem" /> of which to determine type.</param>
-        <summary>Implements <see href="http://exslt.org/exsl/functions/object-type/index.html">exsl:object-type</see>.</summary>
+        <summary>Implements <see href="https://exslt.github.io/exsl/functions/object-type/index.html">exsl:object-type</see>.</summary>
         <returns>Object type as <see cref="T:System.String" />.</returns>
         <remarks>To be added.</remarks>
         <forInternalUseOnly />