patch 8.2.5009: fold may not be closeable after appending

Problem:    Fold may not be closeable after appending.
Solution:   Set the fd_small flag to MAYBE. (Brandon Simmons, closes #10471)
diff --git a/src/version.c b/src/version.c
index 36350c3..07f1b5d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -735,6 +735,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    5009,
+/**/
     5008,
 /**/
     5007,