patch 8.2.2749: Vim9: test for error can be a bit flaky

Problem:    Vim9: test for error can be a bit flaky.
Solution:   Increase the wait time a bit.
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 7155e8f..e570210 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -3681,7 +3681,7 @@
         sleep 10m
       endwhile
       # wait for Exit_cb() to be called
-      sleep 100m
+      sleep 200m
   END
   writefile(lines, 'Xdef')
   assert_fails('so Xdef', ['E684:', 'E1012:'])