patch 8.0.0325: packadd test does not clean up symlink

Problem:    Packadd test does not clean up symlink.
Solution:   Delete the link. (Hirohito Higashi)
diff --git a/src/testdir/test_packadd.vim b/src/testdir/test_packadd.vim
index 5433c98..bf00fa2 100644
--- a/src/testdir/test_packadd.vim
+++ b/src/testdir/test_packadd.vim
@@ -98,6 +98,7 @@
 
   set rtp&
   let rtp = &rtp
+  silent !rm top2_dir
 endfunc
 
 " Check command-line completion for 'packadd'