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/test103.in b/src/testdir/test103.in
index 7c7591e..a4c8084 100644
--- a/src/testdir/test103.in
+++ b/src/testdir/test103.in
@@ -1,6 +1,7 @@
 Test for visual mode not being reset causing E315 error.
 STARTTEST
 :so small.vim
+:set belloff=all
 :enew
 :let g:msg="Everything's fine."
 :function! TriggerTheProblem()