ref-manual: Fixing whitespace.

(From yocto-docs rev: 5ab12447d14ca7054ae44283ec858464c9b04244)

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

documentation/ref-manual/ref-classes.xml

@@ -1231,7 +1231,7 @@
         Use the
         <link linkend='var-WARN_QA'><filename>WARN_QA</filename></link> and
         <link linkend='var-ERROR_QA'><filename>ERROR_QA</filename></link>
-         variables to control the behavior of
+        variables to control the behavior of
         these checks at the global level (i.e. in your custom distro
         configuration).
         However, to skip one or more checks in recipes, you should use