[ipc] Don't CHECK legacy IPC message size

Legacy IPC was switched to BigBuffer in https://crrev.com/4c5bd80e
and therefore no longer needs to be capped at a maximum size.

This removes a stale and unnecessary CHECK against the message size.

Bug: 904415
Change-Id: I1934b06bb0adb3e1d1c6425f906d9f32784beb9b
Reviewed-on: https://chromium-review.googlesource.com/c/1333989Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#607784}

ipc/ipc_channel_proxy.cc

@@ -535,10 +535,6 @@ void ChannelProxy::SendInternal(Message* message) {
   Logging::GetInstance()->OnSendMessage(message);
 #endif
 
-  // See https://crbug.com/766032. This is to ensure that senders of oversized
-  // messages can be caught more easily in the wild.
-  CHECK_LE(message->size(), Channel::kMaximumMessageSize);
-
   context_->Send(message);
 }