vim-patch:8.0.1209: still too many old style tests

Problem:    Still too many old style tests.
Solution:   Convert a few more tests to new style. (Yegappan Lakshmanan,
            closes vim/vim#2230)
53f0c96239

src/nvim/testdir/test_alot.vim

@@ -19,6 +19,7 @@ source test_functions.vim
 source test_ga.vim
 source test_global.vim
 source test_goto.vim
+source test_join.vim
 source test_jumps.vim
 source test_fileformat.vim
 source test_filetype.vim