patch 8.2.2328: some test files may not be deleted

Problem:    Some test files may not be deleted.
Solution:   Add a delete() call, correct name. (Dominique Pellé, closes #7654)
diff --git a/src/testdir/test_clientserver.vim b/src/testdir/test_clientserver.vim
index f838e22..6a73d93 100644
--- a/src/testdir/test_clientserver.vim
+++ b/src/testdir/test_clientserver.vim
@@ -81,6 +81,7 @@
   call writefile(['one', 'two'], 'Xclientfile')
   call system(cmd)
   call WaitForAssert({-> assert_equal('two', remote_expr(name, "getline(2)", "", 2))})
+  call delete('Xclientfile')
 
   " Expression evaluated locally.
   if v:servername == ''