Revert of [tab_grid] Hack-in border for active tab.

ios/clean/chrome/browser/ui/tab_grid/tab_grid_tab_cell.h

Index: ios/clean/chrome/browser/ui/tab_grid/tab_grid_tab_cell.h
diff --git a/ios/clean/chrome/browser/ui/tab_grid/tab_grid_tab_cell.h b/ios/clean/chrome/browser/ui/tab_grid/tab_grid_tab_cell.h
index cc9dc5fe0409869714e0f8dfc3a2e8c08f086b1c..c42d8ed97efa9fd7c6560d78a4c163a05de65f2a 100644
--- a/ios/clean/chrome/browser/ui/tab_grid/tab_grid_tab_cell.h
+++ b/ios/clean/chrome/browser/ui/tab_grid/tab_grid_tab_cell.h
@@ -11,13 +11,12 @@
 
 #import <UIKit/UIKit.h>
 
-#import "ios/chrome/browser/ui/tab_switcher/tab_switcher_panel_cell.h"
+// Placeholder cell implementation for use in the tab grid.
+// A square cell with rounded corners and a label placed in the center.
+@interface TabGridTabCell : UICollectionViewCell
 
-// Cell represents a tab for use in the tab grid. It has a title, favicon,
-// screenshot image, and close button. Cell selection is represented by a border
-// highlight in the tintColor.
-// PLACEHOLDER: Create custom implemementation rather than subclassing.
-@interface TabGridTabCell : TabSwitcherLocalSessionCell
+// The label in the center of the tab cell.
+@property(nonatomic, readonly) UILabel* label;
 
 @end