docs: CIFS: remove a spam-site URL

protocolfreedom.org may have one contained something useful, but now it
wants to sell us new credit cards.  Take it out.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/cifs/usage.rst

@@ -16,8 +16,7 @@ standard for interoperating between Macs and Windows and major NAS appliances.
 
 Please see
 MS-SMB2 (for detailed SMB2/SMB3/SMB3.1.1 protocol specification)
-http://protocolfreedom.org/ and
-https://samba.org/samba/PFIF/
+or https://samba.org/samba/PFIF/
 for more details.