patch 8.2.2488: json_encode() gives generic argument error

Problem:    json_encode() gives generic argument error.
Solution:   Mention the type that can't be encoded. (issue #7802)
diff --git a/src/version.c b/src/version.c
index d07c0e3..8b5de13 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2488,
+/**/
     2487,
 /**/
     2486,