patch 9.0.0335: checks for Dictionary argument often give a vague error

Problem:    Checks for Dictionary argument often give a vague error message.
Solution:   Give a useful error message. (Yegappan Lakshmanan, closes #11009)
diff --git a/src/testdir/test_window_cmd.vim b/src/testdir/test_window_cmd.vim
index e761c21..0fe0f11 100644
--- a/src/testdir/test_window_cmd.vim
+++ b/src/testdir/test_window_cmd.vim
@@ -745,7 +745,7 @@
 
   only!
   bwipe!
-  call assert_fails('call winrestview(test_null_dict())', 'E474:')
+  call assert_fails('call winrestview(test_null_dict())', 'E1297:')
 endfunc
 
 func Test_relative_cursor_position_after_move_and_resize()
@@ -946,7 +946,7 @@
   call assert_equal(view, winsaveview())
 
   bwipe!
-  call assert_fails('call winrestview(test_null_dict())', 'E474:')
+  call assert_fails('call winrestview(test_null_dict())', 'E1297:')
 endfunc
 
 func Test_win_splitmove()
@@ -977,7 +977,7 @@
   call assert_equal(bufname(winbufnr(2)), 'b')
   call assert_equal(bufname(winbufnr(3)), 'a')
   call assert_equal(bufname(winbufnr(4)), 'd')
-  call assert_fails('call win_splitmove(winnr(), winnr("k"), test_null_dict())', 'E474:')
+  call assert_fails('call win_splitmove(winnr(), winnr("k"), test_null_dict())', 'E1297:')
   only | bd
 
   call assert_fails('call win_splitmove(winnr(), 123)', 'E957:')