Add link to current_schemas in config.sgml

Hi folks,

This is just a quick docs patch to add a link to the mention of the
current_schemas function from 18.10.1. Statement Behavior.

The function must be called with one boolean argument, the meaning of
which isn't clear until you read the description in 9.23.

I also removed the parentheses after the function name as this was a)
misleading the reader into thinking the function could be called
without arguments and b) inconsistent with the style for referring to
functions elsewhere in the chapter.

Cheers,
BJ

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 3981969..c0ba5a5 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4485,10 +4485,11 @@ COPY postgres_log FROM
'/full/path/to/logfile.csv' WITH csv;
        <para>
         The current effective value of the search path can be examined
         via the <acronym>SQL</acronym> function
-        <function>current_schemas()</>.  This is not quite the same as
-        examining the value of <varname>search_path</varname>, since
-        <function>current_schemas()</> shows how the items
-        appearing in <varname>search_path</varname> were resolved.
+        <function>current_schemas</> (see <xref linkend="functions-info">).
+        This is not quite the same as examining the value of
+        <varname>search_path</varname>, since <function>current_schemas</>
+        shows how the items appearing in <varname>search_path</varname> were
+        resolved.
        </para>

        <para>