MINOR: quic: Typo fix for ACK_ECN frame

Wrong name displayed by TRACE().

Must be backported to 2.7.
diff --git a/src/quic_frame.c b/src/quic_frame.c
index 2528dec..f569c9f 100644
--- a/src/quic_frame.c
+++ b/src/quic_frame.c
@@ -31,7 +31,7 @@
 	case QUIC_FT_ACK:
 		return "ACK";
 	case QUIC_FT_ACK_ECN:
-		return "ACK_ENC";
+		return "ACK_ECN";
 	case QUIC_FT_RESET_STREAM:
 		return "RESET_STREAM";
 	case QUIC_FT_STOP_SENDING: