Delete unused class MockDelayable

Unused since cl  https://webrtc-review.googlesource.com/c/src/+/218605

Bug: None
Change-Id: Iea0641c3791867679d08a317a5a78c0e75436827
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/223060
Commit-Queue: Niels Moller <nisse@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34332}

pc/test/mock_delayable.h

@@ -1,36 +0,0 @@
-/*
- *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#ifndef PC_TEST_MOCK_DELAYABLE_H_
-#define PC_TEST_MOCK_DELAYABLE_H_
-
-#include <stdint.h>
-
-#include "absl/types/optional.h"
-#include "media/base/delayable.h"
-#include "test/gmock.h"
-
-namespace webrtc {
-
-class MockDelayable : public cricket::Delayable {
- public:
-  MOCK_METHOD(bool,
-              SetBaseMinimumPlayoutDelayMs,
-              (uint32_t ssrc, int delay_ms),
-              (override));
-  MOCK_METHOD(absl::optional<int>,
-              GetBaseMinimumPlayoutDelayMs,
-              (uint32_t ssrc),
-              (const, override));
-};
-
-}  // namespace webrtc
-
-#endif  // PC_TEST_MOCK_DELAYABLE_H_