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_ex_mode.vim b/src/testdir/test_ex_mode.vim
index 2e14e01..a660222 100644
--- a/src/testdir/test_ex_mode.vim
+++ b/src/testdir/test_ex_mode.vim
@@ -237,13 +237,12 @@
     call writefile(['done'], 'Xdidexmode')
     qall!
   END
-  call writefile(lines, 'Xexmodescript')
+  call writefile(lines, 'Xexmodescript', 'D')
   call assert_equal(1, RunVim([], [], '-e -s -S Xexmodescript'))
   call assert_equal(['done'], readfile('Xdidexmode'))
 
   call delete('logfile')
   call delete('Xdidexmode')
-  call delete('Xexmodescript')
 endfunc
 
 func Test_ex_mode_count_overflow()
@@ -257,12 +256,11 @@
     call writefile(['done'], 'Xdidexmode')
     qall!
   END
-  call writefile(lines, 'Xexmodescript')
+  call writefile(lines, 'Xexmodescript', 'D')
   call assert_equal(1, RunVim([], [], '-e -s -S Xexmodescript -c qa'))
   call assert_equal(['done'], readfile('Xdidexmode'))
 
   call delete('Xdidexmode')
-  call delete('Xexmodescript')
 endfunc
 
 func Test_ex_mode_large_indent()
@@ -281,11 +279,9 @@
       0norm0V:
       :qall!
   END
-  call writefile(lines, 'Xexmodescript')
+  call writefile(lines, 'Xexmodescript', 'D')
   call assert_equal(1, RunVim([], [], '-u NONE -e -s -S Xexmodescript'))
 
-  call delete('Xexmodescript')
-
   " This may cause a dialog to be displayed for an empty command, ignore it.
   call delete('guidialogfile')
 endfunc