Fix wrong writing order introduced by last commit

chapter06/tar.xml

@@ -40,12 +40,12 @@
   <sect2 role="installation">
     <title>安装 Tar</title>
 
-    <para>准备编译 Tar：</para>
-
     <para>修复 tar-1.31 引入的一个 bug：</para>
  
  <screen><userinput remap="pre">sed -i 's/abort.*/FALLTHROUGH;/' src/extract.c</userinput></screen>
 
+    <para>准备编译 Tar：</para>
+
 <screen><userinput remap="configure">FORCE_UNSAFE_CONFIGURE=1  \
 ./configure --prefix=/usr \
             --bindir=/bin</userinput></screen>