patch 8.0.0433: beeps when running tests

Problem:    Quite a few beeps when running tests.
Solution:   Set 'belloff' for these tests. (Christian Brabandt)
diff --git a/src/testdir/test_alot_utf8.vim b/src/testdir/test_alot_utf8.vim
index 90b2aab..3022da3 100644
--- a/src/testdir/test_alot_utf8.vim
+++ b/src/testdir/test_alot_utf8.vim
@@ -5,6 +5,7 @@
 " runtest.vim.  Checking for the multi_byte feature is in the individual
 " files, so that they can be run by themselves.
 
+set belloff=all
 source test_expr_utf8.vim
 source test_matchadd_conceal_utf8.vim
 source test_regexp_utf8.vim