patch 8.2.3986: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/map.c b/src/map.c
index cebd43a..336425a 100644
--- a/src/map.c
+++ b/src/map.c
@@ -2374,7 +2374,7 @@
     rhs = dict_get_string(d, (char_u *)"rhs", FALSE);
     if (lhs == NULL || lhsraw == NULL || rhs == NULL)
     {
-	emsg(_("E460: entries missing in mapset() dict argument"));
+	emsg(_(e_entries_missing_in_mapset_dict_argument));
 	return;
     }
     orig_rhs = rhs;