Remove unused headers from ios/web/public/web_state

This CL removes web_state_observer.h and web_state.h from
ios/web/public/web_state which are no longer used in downlstream repo
(downstream code was switched to use files from ios/web/public).

Bug: 942244
Change-Id: I1480b115343735a69347578cfd0628f983c069ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1816807
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Auto-Submit: Eugene But <eugenebut@chromium.org>
Reviewed-by: Yi Su <mrsuyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698929}

ios/web/public/web_state/web_state.h

-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_H_
-#define IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_H_
-
-// TODO(crbug.com/942244): Remove this header after downstream code
-// stopped including ios/web/public/web_state/web_state.h
-
-#import "ios/web/public/web_state.h"
-
-#endif  // IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_H_

ios/web/public/web_state/web_state_observer.h

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_OBSERVER_H_
-#define IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_OBSERVER_H_
-
-// TODO(crbug.com/942244): Remove this header after downstream code
-// stopped including ios/web/public/web_state/web_state.h
-
-#include "ios/web/public/web_state_observer.h"
-
-#endif  // IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_OBSERVER_H_