ref-manual: Minor edits to "bulid/downloads/".

(From yocto-docs rev: 83528239bc84f503e0d3a9f50160d9f2a8b669af)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/ref-structure.xml

@@ -300,8 +300,9 @@
         <title><filename>build/downloads/</filename></title>
 
         <para>
-            This directory is used for the upstream source tarballs.
-            The directory can be reused by multiple builds or moved to another location.
+            This directory contains downloaded upstream source tarballs.
+            You can use reuse the directory for multiple builds or move
+            the directory to another location.
             You can control the location of this directory through the
             <filename><link linkend='var-DL_DIR'>DL_DIR</link></filename> variable.
         </para>