patch 9.0.0637: syntax of commands in Vim9 script depends on +eval feature

Problem:    Syntax of commands in Vim9 script depends on +eval feature.
Solution:   Use same syntax with and without the +eval feature.
diff --git a/src/errors.h b/src/errors.h
index 868ed57..3fa2db1 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -2713,8 +2713,10 @@
 	INIT(= N_("E1048: Item not found in script: %s"));
 EXTERN char e_item_not_exported_in_script_str[]
 	INIT(= N_("E1049: Item not exported in script: %s"));
+#endif
 EXTERN char e_colon_required_before_range_str[]
 	INIT(= N_("E1050: Colon required before a range: %s"));
+#ifdef FEAT_EVAL
 EXTERN char e_wrong_argument_type_for_plus[]
 	INIT(= N_("E1051: Wrong argument type for +"));
 EXTERN char e_cannot_declare_an_option[]