patch 8.2.4611: typos in tests; one lua line not covered by test

Problem:    Typos in tests; one lua line not covered by test.
Solution:   Fix typos. Add test case. (Dominique Pellé, closes #9994)
diff --git a/src/testdir/test_digraph.vim b/src/testdir/test_digraph.vim
index 9cb946c..8420b53 100644
--- a/src/testdir/test_digraph.vim
+++ b/src/testdir/test_digraph.vim
@@ -51,7 +51,7 @@
   call Put_Dig("'e")
   call Put_Dig("b'") " not defined
   call assert_equal(["á", "é", "'"], getline(line('.')-2,line('.')))
-  " Cicumflex
+  " Circumflex
   call Put_Dig("a>")
   call Put_Dig(">e")
   call Put_Dig("b>") " not defined