ref-manual: Grammar fix in "meta/recipes-support/".

(From yocto-docs rev: df3a86f206157a340fef166050f8b0ca18c7c440)

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

@@ -717,8 +717,9 @@
         <title><filename>meta/recipes-support/</filename></title>
 
         <para>
-            This directory contains recipes that used by other recipes, but that are not directly
-            included in images (i.e. dependencies of other recipes).
+            This directory contains recipes used by other recipes, but that are
+            not directly included in images (i.e. dependencies of other
+            recipes).
         </para>
     </section>