Add bool to btree_gist documentation

Commit 57e3c51 added bool opclass to btree_gist, but update the list of
data types in docs to reflect this change.

Reported-by: Pavel Luzanov
Discussion: https://postgr.es/m/CAE2gYzyDKJBZngssR84VGZEN=Ux=V9FV23QfPgo+7-yYnKKg4g@mail.gmail.com

Author: tvondra

doc/src/sgml/btree-gist.sgml

@@ -17,7 +17,7 @@
   <type>oid</type>, <type>money</type>, <type>char</type>,
   <type>varchar</type>, <type>text</type>, <type>bytea</type>, <type>bit</type>,
   <type>varbit</type>, <type>macaddr</type>, <type>macaddr8</type>, <type>inet</type>,
-  <type>cidr</type>, <type>uuid</type>, and all <type>enum</type> types.
+  <type>cidr</type>, <type>uuid</type>, <type>bool</type> and all <type>enum</type> types.
  </para>
 
  <para>