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/vim9compile.c b/src/vim9compile.c
index 265ea66..3a70f7a 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -1394,7 +1394,7 @@
 		    if (is_decl)
 		    {
 			if (script_namespace)
-			    semsg(_(e_cannot_declare_script_variable_in_function),
+			    semsg(_(e_cannot_declare_script_variable_in_function_str),
 								lhs->lhs_name);
 			else
 			    semsg(_(e_variable_already_declared_in_script_str),