patch 8.2.2709: the GTK GUI has a gap next to the scrollbar

Problem:    The GTK GUI has a gap next to the scrollbar.
Solution:   Calculate the scrollbar padding for GTK. (closes #8027)
diff --git a/src/version.c b/src/version.c
index 2b0955c..8a95e67 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2709,
+/**/
     2708,
 /**/
     2707,