[reland] Comment unused variables in implemented functions

Compiling webrtc with `-Werror=unused-parameters` is failling duo to
those parameters.
Also, it shouldn't harm us to put those in comment for code readability as
well.

NOTE: This time I made sure to iterate over the C files in the
audio_processing folder and compile them using gcc.
On the original CL that was reverted - that failed with the same error
Danil mentioned. This time it seems fine.
I'll make sure to run the same script on the rest of my CLs for sanity

Bug: webrtc:370878648
Change-Id: I83cea3a08777e21d26a95bcad503a2d1b74566eb
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/364537
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Dor Hen <dorhen@meta.com>
Cr-Commit-Position: refs/heads/main@{#43249}
diff --git a/api/rtp_sender_interface.h b/api/rtp_sender_interface.h
index aa2eb6f..9afe3e3 100644
--- a/api/rtp_sender_interface.h
+++ b/api/rtp_sender_interface.h
@@ -119,7 +119,7 @@
   // Default implementation of SetFrameTransformer.
   // TODO: bugs.webrtc.org/15929 - remove when all implementations are good
   void SetFrameTransformer(rtc::scoped_refptr<FrameTransformerInterface>
-                               frame_transformer) override {}
+                           /* frame_transformer */) override {}
 
  protected:
   ~RtpSenderInterface() override = default;