patch 8.2.4412: translation cleanup script does not remove empty lines at end

Problem:    Translation cleanup script does not remove empty lines at end.
Solution:   Remove empty lines at the end. (Ken Takata, closes #9794)
diff --git a/src/po/cleanup.vim b/src/po/cleanup.vim
index b27d880..4bb7ae7 100644
--- a/src/po/cleanup.vim
+++ b/src/po/cleanup.vim
@@ -18,7 +18,9 @@
 silent g/^msgid"/s//msgid "/
 silent g/^msgstr ""\(\n"\)\@!/?^msgid?,.s/^/#\~ /
 
+" clean up empty lines
 silent g/^\n\n\n/.d
+silent! %s/\n\+\%$//
 
 if s:was_diff
   setl diff