patch 8.0.1333: some tests are run twice

Problem:    Some tests are run twice.
Solution:   Invoked most utf8 tests only from test_alot_utf8. (Yegappan
            Lakshmanan, closes #2369)
diff --git a/src/testdir/test_alot_utf8.vim b/src/testdir/test_alot_utf8.vim
index 13e227b..648d806 100644
--- a/src/testdir/test_alot_utf8.vim
+++ b/src/testdir/test_alot_utf8.vim
@@ -7,8 +7,11 @@
 
 source test_charsearch_utf8.vim
 source test_expr_utf8.vim
+source test_listlbr_utf8.vim
 source test_matchadd_conceal_utf8.vim
+source test_mksession_utf8.vim
 source test_regexp_utf8.vim
 source test_source_utf8.vim
+source test_startup_utf8.vim
 source test_utf8.vim
 source test_utf8_comparisons.vim