patch 8.2.3971: build fails

Problem:    Build fails.
Solution:   Use the right error message name.
diff --git a/src/version.c b/src/version.c
index 26ecf4c..86c7a47 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3971,
+/**/
     3970,
 /**/
     3969,