doc: Fix typo in section for custom pgstats

Per offline report from Erik Rijkers.

diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index fbdbdbd883fc1fe595cd7186baf7db5ab7730b78..9bc23a9a9388451bb81297bd05a2692fce44b60f 100644 (file)
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -3868,7 +3868,7 @@ extern bool InjectionPointDetach(const char *name);
     <title>Custom Cumulative Statistics</title>
 
     <para>
-     Is is possible for add-ins written in C-language to use custom types
+     It is possible for add-ins written in C-language to use custom types
      of cumulative statistics registered in the
      <link linkend="monitoring-stats-setup">Cumulative Statistics System</link>.
     </para>