docs: Fix list of object types pg_table_is_visible() can handle.

Materialized views and foreign tables were missing from the list,
probably because they are newer than the other object types that were
mentioned.

Etsuro Fujita

Author: robertmhaas

doc/src/sgml/func.sgml

@@ -15574,8 +15574,9 @@ SELECT relname FROM pg_class WHERE pg_table_is_visible(oid);
    <para>
     Each function performs the visibility check for one type of database
     object.  Note that <function>pg_table_is_visible</function> can also be used
-    with views, indexes and sequences; <function>pg_type_is_visible</function>
-    can also be used with domains. For functions and operators, an object in
+    with views, materialized views, indexes, sequences and foreign tables;
+    <function>pg_type_is_visible</function> can also be used with domains.
+    For functions and operators, an object in
     the search path is visible if there is no object of the same name
     <emphasis>and argument data type(s)</> earlier in the path.  For operator
     classes, both name and associated index access method are considered.