patch 9.0.1387: scrollbar test sporadically fails

Problem:    Scrollbar test sporadically fails.
Solution:   Mark the scrollbar test as flaky. (Christian Brabandt,
            closes #12113)
diff --git a/src/testdir/test_gui.vim b/src/testdir/test_gui.vim
index 6b5e12c..809dd35 100644
--- a/src/testdir/test_gui.vim
+++ b/src/testdir/test_gui.vim
@@ -718,8 +718,11 @@
 endfunc
 
 func Test_scrollbars()
-  new
+  " this test sometimes fails on CI
+  let g:test_is_flaky = 1
+
   " buffer with 200 lines
+  new
   call setline(1, repeat(['one', 'two'], 100))
   set guioptions+=rlb
 
diff --git a/src/version.c b/src/version.c
index 994ddb9..e590919 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1387,
+/**/
     1386,
 /**/
     1385,