pw_rpc: Update docs to reference FixedMtuChannelOutput

Change-Id: If2a048d0d89d35ba2a8e5ed09db98e519790a11c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/109376
Pigweed-Auto-Submit: Erik Gilling <konkers@google.com>
Reviewed-by: Anthony DiGirolamo <tonymd@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_rpc/docs.rst b/pw_rpc/docs.rst
index 59e2605..4744668 100644
--- a/pw_rpc/docs.rst
+++ b/pw_rpc/docs.rst
@@ -291,7 +291,7 @@
   // pw_rpc server to use HDLC over UART; projects not using UART and HDLC must
   // adapt this as necessary.
   pw::stream::SysIoWriter writer;
-  pw::rpc::RpcChannelOutput<kMaxTransmissionUnit> hdlc_channel_output(
+  pw::rpc::FixedMtuChannelOutput<kMaxTransmissionUnit> hdlc_channel_output(
       writer, pw::hdlc::kDefaultRpcAddress, "HDLC output");
 
   pw::rpc::Channel channels[] = {