patch 8.2.4476: operator name spelled wrong

Problem:    Operator name spelled wrong.
Solution:   Change trinary to ternary. (Goc Dundar, closes #9850)
diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 7a998bc..40c1701 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -43,7 +43,7 @@
   call assert_false(has('patch-9.9.1'))
 endfunc
 
-func Test_op_trinary()
+func Test_op_ternary()
   let lines =<< trim END
       call assert_equal('yes', 1 ? 'yes' : 'no')
       call assert_equal('no', 0 ? 'yes' : 'no')