patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error

Problem:    Vim9: accidentally using "x" gives a confusing error.
Solution:   Disallow using ":t" in Vim9 script. (issue #6399)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index c01b383..8950f31 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -1628,18 +1628,21 @@
 enddef
 
 def Test_no_insert_xit()
-  call CheckDefExecFailure(['x = 1'], 'E1100:')
   call CheckDefExecFailure(['a = 1'], 'E1100:')
-  call CheckDefExecFailure(['i = 1'], 'E1100:')
   call CheckDefExecFailure(['c = 1'], 'E1100:')
+  call CheckDefExecFailure(['i = 1'], 'E1100:')
+  call CheckDefExecFailure(['t = 1'], 'E1100:')
+  call CheckDefExecFailure(['x = 1'], 'E1100:')
 
-  CheckScriptFailure(['vim9script', 'x = 1'], 'E1100:')
   CheckScriptFailure(['vim9script', 'a = 1'], 'E488:')
   CheckScriptFailure(['vim9script', 'a'], 'E1100:')
-  CheckScriptFailure(['vim9script', 'i = 1'], 'E488:')
-  CheckScriptFailure(['vim9script', 'i'], 'E1100:')
   CheckScriptFailure(['vim9script', 'c = 1'], 'E488:')
   CheckScriptFailure(['vim9script', 'c'], 'E1100:')
+  CheckScriptFailure(['vim9script', 'i = 1'], 'E488:')
+  CheckScriptFailure(['vim9script', 'i'], 'E1100:')
+  CheckScriptFailure(['vim9script', 't'], 'E1100:')
+  CheckScriptFailure(['vim9script', 't = 1'], 'E1100:')
+  CheckScriptFailure(['vim9script', 'x = 1'], 'E1100:')
 enddef
 
 def IfElse(what: number): string