Revert "Add ability to specify if rate controller of video encoder is trusted."

This reverts commit 3e335d1423cab06cca8cdb4f1fadb0b16c9e7d38.

Reason for revert: breaks downstream project

Original change's description:
> Add ability to specify if rate controller of video encoder is trusted.
>
> If rate controller is trusted, we disable the frame dropper in the
> media optimization module.
>
> Bug: webrtc:9722
> Change-Id: I821f21fd74a400ee9d5aa3f6b42d4e569033acbe
> Reviewed-on: https://webrtc-review.googlesource.com/c/105020
> Commit-Queue: Erik Språng <sprang@webrtc.org>
> Reviewed-by: Per Kjellander <perkj@webrtc.org>
> Reviewed-by: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
> Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#25107}

TBR=brandtr@webrtc.org,ilnik@webrtc.org,nisse@webrtc.org,sprang@webrtc.org,perkj@webrtc.org

Change-Id: Ifdb0aae684894854a184ec1e7423a7c62e7ba237
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9722
Reviewed-on: https://webrtc-review.googlesource.com/c/105360
Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25117}

api/BUILD.gn

@@ -515,19 +515,6 @@ if (rtc_include_tests) {
     ]
   }
 
-  rtc_source_set("mock_video_encoder") {
-    testonly = true
-    sources = [
-      "test/mock_video_encoder.cc",
-      "test/mock_video_encoder.h",
-    ]
-
-    deps = [
-      "../api/video_codecs:video_codecs_api",
-      "../test:test_support",
-    ]
-  }
-
   rtc_source_set("rtc_api_unittests") {
     testonly = true