(Aux-Item Types): Document that faq-text may be set on letterboxes.

doc/Protocol-A.texi

@@ -8409,11 +8409,11 @@ This aux-item can only be set by the supervisor of a conference or the
 server administrator.  The creator cannot be hidden.
 
 
-@item faq-text [14] (conference, server)
+@item faq-text [14] (conference, letterbox, server)
 
-Data is a decimal text number, which is a FAQ for the conference (or
-server).  Creating an item of this type automatically causes creation of
-a faq-for-conf item.
+Data is a decimal text number, which is a FAQ for the conference,
+letterbox or server.  Creating an item of this type automatically
+causes creation of a faq-for-conf item.
 
 This item can only be set by the supervisor or server administrator.  The
 hide-creator, secret, and inherit bits are automatically cleared.