patch 8.1.1590: popup window test fails

Problem:    Popup window test fails.
Solution:   Add "scrollbar" to expected result.
diff --git a/src/version.c b/src/version.c
index 34af0de..5db753c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1590,
+/**/
     1589,
 /**/
     1588,