patch 8.1.1216: mouse middle click is not tested

Problem:    Mouse middle click is not tested.
Solution:   Add a test. (Dominique Pelle, closes #4310)
diff --git a/src/version.c b/src/version.c
index 0d2e344..5337512 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1216,
+/**/
     1215,
 /**/
     1214,