patch 8.2.3226: new digraph functions use old naming scheme

Problem:    New digraph functions use old naming scheme.
Solution:   Use the digraph_ prefix. (Hirohito Higashi, closes #8580)
diff --git a/src/errors.h b/src/errors.h
index d088168..7e4a465 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -610,8 +610,8 @@
 	INIT(= N_("E1214: Digraph must be just two characters: %s"));
 EXTERN char e_digraph_argument_must_be_one_character_str[]
 	INIT(= N_("E1215: Digraph must be one character: %s"));
-EXTERN char e_setdigraphlist_argument_must_be_list_of_lists_with_two_items[]
-	INIT(= N_("E1216: setdigraphlist() argument must be a list of lists with two items"));
+EXTERN char e_digraph_setlist_argument_must_be_list_of_lists_with_two_items[]
+	INIT(= N_("E1216: digraph_setlist() argument must be a list of lists with two items"));
 #endif
 EXTERN char e_chan_or_job_required_for_argument_nr[]
 	INIT(= N_("E1217: Channel or Job required for argument %d"));