CLEANUP: quic: Comment fix for qc_strm_cpy()

This function never returns a negative value... hopefully because it returns
a size_t!!!
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index 0dfd108..760b9a7 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -2025,8 +2025,7 @@
 }
 
 /* Copy as most as possible STREAM data from <strm_frm> into <strm> stream.
- * Returns the number of bytes copied or -1 if failed. Also update <strm_frm> frame
- * to reflect the data which have been consumed.
+ * Also update <strm_frm> frame to reflect the data which have been consumed.
  */
 static size_t qc_strm_cpy(struct buffer *buf, struct quic_stream *strm_frm)
 {