patch 8.2.1204: Vim9: true and false not recognized in Vim9 script

Problem:    Vim9: true and false not recognized in Vim9 script.
Solution:   Recognize true and false.
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index ede464e..cba41e3 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -1024,6 +1024,19 @@
   call CheckDefFailure(['v:none = 22'], 'E46:')
 enddef
 
+def Test_expr7_special_vim9script()
+  let lines =<< trim END
+      vim9script
+      let t = true
+      let f = false
+      assert_equal(v:true, true)
+      assert_equal(true, t)
+      assert_equal(v:false, false)
+      assert_equal(false, f)
+  END
+  CheckScriptSuccess(lines)
+enddef
+
 def Test_expr7_list()
   " list
   assert_equal(g:list_empty, [])