patch 8.2.4510: Vim9: shortening commands leads to confusing script

Problem:    Vim9: shortening commands leads to confusing script.
Solution:   In Vim9 script require at least ":cont" for ":continue", "const"
            instead of "cons", "break" instead of "brea", "catch" instead of
            "cat", "else" instead of "el" "elseif" instead of "elsei" "endfor"
            instead of "endfo" "endif" instead of "en" "endtry" instead of
            "endt", "finally" instead of "fina", "throw" instead of "th",
            "while" instead of "wh".
diff --git a/src/errors.h b/src/errors.h
index 82708d3..9a2c394 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -2761,9 +2761,9 @@
 #endif
 EXTERN char e_yank_register_changed_while_using_it[]
 	INIT(= N_("E1064: Yank register changed while using it"));
+EXTERN char e_command_cannot_be_shortened[]
+	INIT(= N_("E1065: Command cannot be shortened: %s"));
 #ifdef FEAT_EVAL
-EXTERN char e_must_use_var_instead_of_va[]
-	INIT(= N_("E1065: Must use :var instead of :va"));
 EXTERN char e_cannot_declare_a_register_str[]
 	INIT(= N_("E1066: Cannot declare a register: %s"));
 EXTERN char e_separator_mismatch_str[]