Remove parentheses from mention of current_schemas function.

This is more consistent with what we do elsewhere, and hopefully avoids
creating the perception that current_schemas takes no arguments.

As suggested by Brendan Jurd

doc/src/sgml/config.sgml

@@ -4491,11 +4491,11 @@ 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()</>
+        <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
+        <function>current_schemas</> shows how the items
         appearing in <varname>search_path</varname> were resolved.
        </para>