patch 8.2.4360: Vim9: allowing use of "s:" leads to inconsistencies

Problem:    Vim9: allowing use of "s:" leads to inconsistencies.
Solution:   Disallow using "s:" in Vim9 script at the script level.
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index 1e61853..ec71836 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -300,11 +300,11 @@
       vim9script
       import autoload 'autoscript.vim'
 
-      def s:AutoloadFunc()
+      def AutoloadFunc()
         &operatorfunc = autoscript.Opfunc
       enddef
 
-      var res = execute('disass s:AutoloadFunc')
+      var res = execute('disass AutoloadFunc')
       assert_match('<SNR>\d*_AutoloadFunc.*' ..
             '&operatorfunc = autoscript.Opfunc\_s*' ..
             '0 AUTOLOAD autoscript#Opfunc\_s*' ..