patch 9.0.1009: test for catch after interrupt is flaky on MS-Windows

Problem:    Test for catch after interrupt is flaky on MS-Windows.
Solution:   Mark the test as flaky.
diff --git a/src/testdir/test_vimscript.vim b/src/testdir/test_vimscript.vim
index 5599754..295a03b 100644
--- a/src/testdir/test_vimscript.vim
+++ b/src/testdir/test_vimscript.vim
@@ -6017,6 +6017,9 @@
 
 " interrupt right before a catch is invoked inside a function.
 func Test_ignore_catch_after_intr_2()
+  " for unknown reasons this test sometimes fails on MS-Windows.
+  let g:test_is_flaky = 1
+
   XpathINIT
   func F()
     try