Fix documentation from recent test_custom_stats commit

From af09177a2ed4a0a715492e06b20a70a62295b3b7 Mon Sep 17 00:00:00 2001
From: Ubuntu <ubuntu@ip-172-31-46-230.ec2.internal>
Date: Sun, 14 Dec 2025 01:29:35 +0000
Subject: [PATCH v1 1/1] Fix incorrect documentation for test_custom_stats

In 31280d96a6, the reference to the test_custom_stats module
should have been added under "Custom Cumulative Statistics"
section instead of the "Injection Points" section.

Discussion: https://www.postgresql.org/message-id/aTZxqzPWr0wMVLq2%40paquier.xyz
---
 doc/src/sgml/xfunc.sgml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index 7c76ab8c349..2de3309267d 100644
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -3935,7 +3935,7 @@ extern bool InjectionPointDetach(const char *name);
 
     <para>
      An example can be found in
-     <filename>src/test/modules/test_custom_stats</filename> in the PostgreSQL
+     <filename>src/test/modules/injection_points</filename> in the PostgreSQL
      source tree.
     </para>
 
@@ -4005,7 +4005,7 @@ extern PgStat_Kind pgstat_register_kind(PgStat_Kind kind,
 
     <para>
      An example describing how to register and use custom statistics can be
-     found in <filename>src/test/modules/injection_points</filename>.
+     found in <filename>src/test/modules/test_custom_stats</filename>.
     </para>
    </sect2>
 
-- 
2.43.0