vim-patch:8.0.0433: beeps when running tests

Problem:    Quite a few beeps when running tests.
Solution:   Set 'belloff' for these tests. (Christian Brabandt)

c3c766ea8c

src/nvim/testdir/test_digraph.vim

@@ -3,6 +3,7 @@
 if !has("digraphs") || !has("multi_byte")
   finish
 endif
+set belloff=all
 
 func! Put_Dig(chars)
   exe "norm! o\<c-k>".a:chars