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_visual.vim b/src/testdir/test_visual.vim
index 227da87..371fab5 100644
--- a/src/testdir/test_visual.vim
+++ b/src/testdir/test_visual.vim
@@ -3,6 +3,8 @@
   finish
 endif
 
+set belloff=all
+
 func Test_block_shift_multibyte()
   " Uses double-wide character.
   if !has('multi_byte')