patch 8.2.2112: running tests may leave some files behind

Problem:    Running tests may leave some files behind.
Solution:   Delete the right files.  Fix a few typos. (Dominique Pellé,
            closes #7436
diff --git a/src/testdir/test_messages.vim b/src/testdir/test_messages.vim
index 158e94b..4f8c751 100644
--- a/src/testdir/test_messages.vim
+++ b/src/testdir/test_messages.vim
@@ -323,7 +323,7 @@
 
   " clean up
   call StopVimInTerminal(buf)
-  call delete('Xtest_diff_rnu')
+  call delete('Xtest_quit_message')
 endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab