patch 8.2.4361: Vim9: some tests fail

Problem:    Vim9: some tests fail.
Solution:   Fix the tests, mostly by removing "s:".
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 6baba97..e2820db 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -2798,7 +2798,7 @@
   call assert_fails('let l:.trim = {x -> " " .. x}', 'E704:')
   let lines =<< trim END
     vim9script
-    var s:trim = (x) => " " .. x
+    var trim = (x) => " " .. x
   END
   call v9.CheckScriptFailure(lines, 'E704:')