patch 8.2.3251: listing builtin_gui as an available terminal is confusing

Problem:    Listing builtin_gui as an available terminal is confusing.
Solution:   Do not list builtin_gui. (Christian Brabandt, closes #8669,
            closes #8661)
diff --git a/src/version.c b/src/version.c
index f324f3d..046d1e7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3251,
+/**/
     3250,
 /**/
     3249,