patch 8.1.1601: missing changes to popup window test file

Problem:    Missing changes to popup window test file.
Solution:   Add those changes.
diff --git a/src/version.c b/src/version.c
index b34071e..55c62df 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1601,
+/**/
     1600,
 /**/
     1599,