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/src/stats.c b/src/stats.c
index be8bc64..5ed96d6 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -4138,7 +4138,7 @@
 
 	if (appctx->st0 == STAT_HTTP_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;