MINOR: htx: Rename HTX_FL_EOI flag into HTX_FL_EOM

The HTX_FL_EOI flag is not well named. For now, it is not very used. But
that will change. It will replace the EOM block. Thus, it is renamed.
diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index 364d4b6..cfd0d99 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -1226,7 +1226,7 @@
 
 		case PROMEX_ST_DONE:
 			/* Don't add TLR because mux-h1 will take care of it */
-			res_htx->flags |= HTX_FL_EOI; /* no more data are expected. Only EOM remains to add now */
+			res_htx->flags |= HTX_FL_EOM; /* no more data are expected. Only EOM remains to add now */
 			if (!htx_add_endof(res_htx, HTX_BLK_EOM)) {
 				si_rx_room_blk(si);
 				goto out;