Remove another obsolete sed

was r11549.

chapter06/texinfo.xml

@@ -40,10 +40,6 @@
   <sect2 role="installation">
     <title>安装 Texinfo</title>
 
-    <para>修复一个在退化测试中产生大量失败的文件：</para>
-
-<screen><userinput remap="pre">sed -i '5481,5485 s/({/(\\{/' tp/Texinfo/Parser.pm</userinput></screen>
-
     <para>准备安装 Texinfo：</para>
 
 <screen><userinput remap="configure">./configure --prefix=/usr --disable-static</userinput></screen>