re-deprecate StandardAuthScheme.KERBEROS

Author: stoty

httpclient5/src/main/java/org/apache/hc/client5/http/auth/StandardAuthScheme.java

@@ -71,7 +71,11 @@ private StandardAuthScheme() {
 
     /**
      * Kerberos authentication scheme as defined in RFC 4120.
+     *
+     * @deprecated Do not use. The Kerberos scheme was never standardized, and its
+     * implementation uses the old deprecated non mutual auth capable logic.
      */
+    @Deprecated
     public static final String KERBEROS = "Kerberos";
 
 }