doc: a small improvement about pg_am description

[Yugo NAGATA]

Hi,

When reading the documentation about operator class, I found
the following description:

 The pg_am table contains one row for every index access method. 
 Support for access to regular tables is built into PostgreSQL, 
 but all index access methods are described in pg_am.

It seems to me that this description says pg_am contains only
index access methods but not table methods. I wonder it is missed
to fix this when tableam was supported and other documentation
was changed in b73c3a11963c8bb783993cfffabb09f558f86e37.

Attached is a patch to remove the sentence that starts with
"Support for access to regular tables is ....".

Ragards,
Yugo Nagata

-- 
Yugo NAGATA <nag...@sraoss.co.jp>

diff --git a/doc/src/sgml/xindex.sgml b/doc/src/sgml/xindex.sgml
index c753d8005a..ff73233818 100644
--- a/doc/src/sgml/xindex.sgml
+++ b/doc/src/sgml/xindex.sgml
@@ -30,11 +30,8 @@
 
   <para>
    The <classname>pg_am</classname> table contains one row for every
-   index method (internally known as access method).  Support for
-   regular access to tables is built into
-   <productname>PostgreSQL</productname>, but all index methods are
-   described in <classname>pg_am</classname>.  It is possible to add a
-   new index access method by writing the necessary code and
+   index and table method (internally known as access method). It is possible
+   to add a new index access method by writing the necessary code and
    then creating an entry in <classname>pg_am</classname> &mdash; but that is
    beyond the scope of this chapter (see <xref linkend="indexam"/>).
   </para>