patch 9.0.1214: file left behind after running tests

Problem:    File left behind after running tests.
Solution:   Delete the file. (Dominique Pellé, closes #11839)
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index cf3d6fc..12fbcb7 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -640,6 +640,7 @@
         \ }, event)
 
   call StopVimInTerminal(buf)
+  call delete('XscrollEvent')
 endfunc
 
 func Test_WinClosed()