patch 8.2.1600: Vim9: cannot use "true" with deepcopy()

Problem:    Vim9: cannot use "true" with deepcopy().
Solution:   Use tv_get_bool_chk(). (closes #6867)
diff --git a/src/testdir/test_listdict.vim b/src/testdir/test_listdict.vim
index 8db7b3f..694ba0a 100644
--- a/src/testdir/test_listdict.vim
+++ b/src/testdir/test_listdict.vim
@@ -348,7 +348,7 @@
   let l[1] = l2
   let l3 = deepcopy(l2)
   call assert_true(l3[1] is l3[2])
-  call assert_fails("call deepcopy([1, 2], 2)", 'E474:')
+  call assert_fails("call deepcopy([1, 2], 2)", 'E1023:')
 endfunc
 
 " Locked variables
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 828dbba..8651ef8 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1272,6 +1272,8 @@
     res += n
   endfor
   assert_equal(6, res)
+
+  dl = deepcopy([1, 2, 3], true)
 enddef
 
 def Test_extend_return_type()