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_vimscript.vim b/src/testdir/test_vimscript.vim
index 3cd42d0..f497498 100644
--- a/src/testdir/test_vimscript.vim
+++ b/src/testdir/test_vimscript.vim
@@ -7475,7 +7475,7 @@
 endfunc
 
 " Test for issue6776              {{{1
-func Test_trinary_expression()
+func Test_ternary_expression()
   try
     call eval('0 ? 0')
   catch