Reword slightly logs generated for index stats in autovacuum

Using "remain" is confusing, as it implies that the index file can
shrink.  Instead, use "in total".

Per discussion with Peter Geoghegan.

Discussion: https://postgr.es/m/CAH2-WzkYgHZzpGOwR14CScJsjaQpvJrEkEfkh_=wGhzLb=yVdQ@mail.gmail.com

src/backend/access/heap/vacuumlazy.c

@@ -703,7 +703,7 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 					continue;
 
 				appendStringInfo(&buf,
-								 _("index \"%s\": pages: %u remain, %u newly deleted, %u currently deleted, %u reusable\n"),
+								 _("index \"%s\": pages: %u in total, %u newly deleted, %u currently deleted, %u reusable\n"),
 								 indnames[i],
 								 stats->num_pages,
 								 stats->pages_newly_deleted,