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/test77.in b/src/testdir/test77.in
index 0dbc4fc..55a1c30 100644
--- a/src/testdir/test77.in
+++ b/src/testdir/test77.in
@@ -10,6 +10,7 @@
 
 STARTTEST
 :so small.vim
+:set belloff=all
 :if !executable("cksum")
 : e! test.ok
 : w! test.out