MINOR: quic: Remove a useless test in quic_get_dgram_dcid()

This test is already done when entering quic_get_dgram_dcid().
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index 0f9987e..23126e7 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -5429,7 +5429,7 @@
 	minlen = long_header ?
 		QUIC_LONG_PACKET_MINLEN : QUIC_SHORT_PACKET_MINLEN + QUIC_HAP_CID_LEN;
 	skip = long_header ? QUIC_LONG_PACKET_DCID_OFF : QUIC_SHORT_PACKET_DCID_OFF;
-	if (end - buf <= minlen || !(*buf & QUIC_PACKET_FIXED_BIT))
+	if (end - buf <= minlen)
 		goto err;
 
 	buf += skip;