[2133] Minor fix

The previous version was slightly misleading, the reader could
understand it the queries would be just slow as answered from the DB,
instead of not answered at all.

doc/guide/bind10-guide.xml

@@ -1543,8 +1543,7 @@ can use various data source backends.
         a boolean value turning the cache on and off (off is the default).
         The second one, <varname>cache-zones</varname>, is a list of zone
         origins to load into in-memory. Remember that zones in the data source
-        not listed here will not be loaded and will not be available from
-        memory.
+        not listed here will not be loaded and will not be available at all.
       </para>
 
       <section id='datasource-types'>