Revert "Fix buffer overflow in ulpfec recovery"

This reverts commit 865feab.

Reason for revert: didn't fix the overlow

Original change's description:
> Fix buffer overflow in ulpfec recovery
> 
> Bug: chromium:856823
> Change-Id: I21fe21789ed3efbf71b5d3e234740a50c7911f6c
> Reviewed-on: https://webrtc-review.googlesource.com/88228
> Reviewed-by: Rasmus Brandt <[email protected]>
> Commit-Queue: Danil Chapovalov <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#23947}

[email protected],[email protected]

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:856823
Change-Id: I095b93ffa1754e1923ab58a7fa61575b6e2fd83a
Reviewed-on: https://webrtc-review.googlesource.com/88720
Reviewed-by: Danil Chapovalov <[email protected]>
Commit-Queue: Danil Chapovalov <[email protected]>
Cr-Commit-Position: refs/heads/master@{#23982}

modules/rtp_rtcp/source/forward_error_correction.cc

@@ -609,8 +609,8 @@ void ForwardErrorCorrection::XorPayloads(const Packet& src,
                                          size_t dst_offset,
                                          Packet* dst) {
   // XOR the payload.
-  RTC_CHECK_LE(kRtpHeaderSize + payload_length, sizeof(src.data));
-  RTC_CHECK_LE(dst_offset + payload_length, sizeof(dst->data));
+  RTC_DCHECK_LE(kRtpHeaderSize + payload_length, sizeof(src.data));
+  RTC_DCHECK_LE(dst_offset + payload_length, sizeof(dst->data));
   for (size_t i = 0; i < payload_length; ++i) {
     dst->data[dst_offset + i] ^= src.data[kRtpHeaderSize + i];
   }
@@ -627,8 +627,7 @@ bool ForwardErrorCorrection::RecoverPacket(const ReceivedFecPacket& fec_packet,
       recovered_packet->seq_num = protected_packet->seq_num;
     } else {
       XorHeaders(*protected_packet->pkt, recovered_packet->pkt);
-      XorPayloads(*protected_packet->pkt,
-                  protected_packet->pkt->length - kRtpHeaderSize,
+      XorPayloads(*protected_packet->pkt, protected_packet->pkt->length,
                   kRtpHeaderSize, recovered_packet->pkt);
     }
   }