patch 9.0.0363: common names in test files causes tests to be flaky

Problem:    Common names in test files causes tests to be flaky.
Solution:   Use more specific names.
diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index 56629d9..ec11494 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -883,7 +883,7 @@
   new
   call setline(1, ['L1'])
   set nowrite
-  call assert_fails('write Xfile', 'E142:')
+  call assert_fails('write Xwrfile', 'E142:')
   set write
   close!
 endfunc