patch 8.1.1446: popup window callback not implemented yet

Problem:    Popup window callback not implemented yet.
Solution:   Implement the callback.
diff --git a/src/version.c b/src/version.c
index 3be4e65..597fb90 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1446,
+/**/
     1445,
 /**/
     1444,