BUG/MINOR: mux-quic: fix POST with abortonclose

Remove CS_EP_EOS set erroneously on qc_rcv_buf().

This fixes POST with abortonclose. Previously, request was preemptively
aborted by haproxy due to the incorrect EOS flag.

For the moment, EOS flag is not set anymore. It should be set to warn
about a premature close from the client.
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 04f0c71..a2d84cd 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -1273,7 +1273,7 @@
 			cs->endp->flags |= CS_EP_ERROR;
 
 		if (fin)
-			cs->endp->flags |= (CS_EP_EOI|CS_EP_EOS);
+			cs->endp->flags |= CS_EP_EOI;
 
 		if (b_size(&qcs->rx.app_buf)) {
 			b_free(&qcs->rx.app_buf);