Revert of Add TabContainer to Showcase

ios/showcase/tab/sc_tab_egtest.mm

-// Copyright 2017 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.
-
-#import <EarlGrey/EarlGrey.h>
-
-#import "ios/showcase/test/showcase_matchers.h"
-#import "ios/showcase/test/showcase_test_case.h"
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
-// Tests for the tab container view controller.
-@interface SCTabTestCase : ShowcaseTestCase
-@end
-
-@implementation SCTabTestCase
-
-// Tests launching TopToolbarTabViewController.
-- (void)testLaunchWithTopToolbar {
-  [[EarlGrey selectElementWithMatcher:grey_text(@"TopToolbarTabViewController")]
-      performAction:grey_tap()];
-  [[EarlGrey selectElementWithMatcher:showcase_matchers::FirstLevelBackButton()]
-      performAction:grey_tap()];
-}
-
-// Tests launching BottomToolbarTabViewController.
-- (void)testLaunchWithBottomToolbar {
-  [[EarlGrey
-      selectElementWithMatcher:grey_text(@"BottomToolbarTabViewController")]
-      performAction:grey_tap()];
-  [[EarlGrey selectElementWithMatcher:showcase_matchers::FirstLevelBackButton()]
-      performAction:grey_tap()];
-}
-
-@end