Update ref/drop_index.sgml-200603

——row116至125，增加英文和中文内容为：
<!--==========================orignal english content==========================
     <para>
      For temporary tables, <command>DROP INDEX</command> is always
      non-concurrent, as no other session can access them, and
      non-concurrent index drop is cheaper.
     </para>
____________________________________________________________________________-->
     <para>
      对于临时表，<command>DROP INDEX</command>始终是非并发的，因为没有其他会话可以访问它们，而且丢弃非并发索引更加便宜。
     </para>

Author: chegong18

postgresql/doc/src/sgml/ref/drop_index.sgml

@@ -113,6 +113,16 @@ ____________________________________________________________________________-->
       的<command>DROP INDEX</command>命令可以在一个事务块内执行，而
       <command>DROP INDEX CONCURRENTLY</command>不能。
      </para>
+<!--==========================orignal english content==========================
+     <para>
+      For temporary tables, <command>DROP INDEX</command> is always
+      non-concurrent, as no other session can access them, and
+      non-concurrent index drop is cheaper.
+     </para>
+____________________________________________________________________________-->
+     <para>
+      对于临时表，<command>DROP INDEX</command>始终是非并发的，因为没有其他会话可以访问它们，而且丢弃非并发索引更加便宜。
+     </para>
     </listitem>
    </varlistentry>