Remove unused KeyboardUI::Show

ash/common/keyboard/keyboard_ui.cc

Index: ash/common/keyboard/keyboard_ui.cc
diff --git a/ash/common/keyboard/keyboard_ui.cc b/ash/common/keyboard/keyboard_ui.cc
index b5f8a5596f177c5d674ed46cedce26fd11213555..aaada086f26f1da8481a8c9a4cd870e9915204f4 100644
--- a/ash/common/keyboard/keyboard_ui.cc
+++ b/ash/common/keyboard/keyboard_ui.cc
@@ -27,10 +27,6 @@ class KeyboardUIImpl : public KeyboardUI, public AccessibilityObserver {
       WmShell::Get()->system_tray_notifier()->RemoveAccessibilityObserver(this);
   }
 
-  // KeyboardUI:
-  void Show() override {
-    keyboard::KeyboardController::GetInstance()->ShowKeyboard(true);
-  }
   void ShowInDisplay(const int64_t display_id) override {
     keyboard::KeyboardController::GetInstance()->ShowKeyboardInDisplay(
         display_id);