patch 9.0.1133: error message names do not match the items

Problem:    Error message names do not match the items.
Solution:   Add "_str" when the text contains "%s".
diff --git a/src/vim9cmds.c b/src/vim9cmds.c
index ed6311b..763d8b3 100644
--- a/src/vim9cmds.c
+++ b/src/vim9cmds.c
@@ -1035,7 +1035,7 @@
 		    goto failed;
 		if (lookup_local(arg, varlen, NULL, cctx) == OK)
 		{
-		    semsg(_(e_variable_already_declared), arg);
+		    semsg(_(e_variable_already_declared_str), arg);
 		    goto failed;
 		}