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_search.vim b/src/testdir/test_search.vim
index 1a114c4..7f4f7e0 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -1,5 +1,6 @@
 " Test for the search command
 
+set belloff=all
 func Test_search_cmdline()
   if !exists('+incsearch')
     return