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.vim b/src/testdir/test_alot.vim
index 4ccff8a..8cbd601 100644
--- a/src/testdir/test_alot.vim
+++ b/src/testdir/test_alot.vim
@@ -1,6 +1,7 @@
 " A series of tests that can run in one Vim invocation.
 " This makes testing go faster, since Vim doesn't need to restart.
 
+set belloff=all
 source test_assign.vim
 source test_autocmd.vim
 source test_changedtick.vim