patch 9.0.0538: manually deleting test temp files

Problem:    Manually deleting test temp files.
Solution:   Add the 'D' flag to writefile().
diff --git a/src/testdir/test_eval_stuff.vim b/src/testdir/test_eval_stuff.vim
index 33ab45f..46ec12d 100644
--- a/src/testdir/test_eval_stuff.vim
+++ b/src/testdir/test_eval_stuff.vim
Binary files differ