[ios] Removes a call to -[UIPickerView showsSelectorIndicator].

This method was deprecated in iOS 13. From the UIKit documentation: "On
iOS 7 and later you cannot customize the picker view’s selection
indicator. The selection indicator is always shown, so setting this
property to NO has no effect."

BUG=1086653

Change-Id: Iac7eaf2b887ebf4a7c6a9cb47c4df1b984e7c6c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2218816Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773165}

ios/chrome/browser/ui/elements/selector_picker_view_controller.mm

@@ -79,7 +79,6 @@ CGFloat kUIPickerFontSize = 26;
   [super viewDidLoad];
   self.view.backgroundColor = [UIColor whiteColor];
 
-  self.pickerView.showsSelectionIndicator = YES;
   self.pickerView.backgroundColor = [UIColor whiteColor];
   self.pickerView.delegate = self;
   self.pickerView.dataSource = self;