patch 8.2.3516: terminal window does not have transparent background

Problem:    Terminal window does not have transparent background when
            'termguicolors' is used.
Solution:   Fix the background color. (closes #2361, closes #9002)
diff --git a/src/version.c b/src/version.c
index f7af2d7..dfe5139 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3516,
+/**/
     3515,
 /**/
     3514,