use shortcut command as key for retrieving shortcut to be deleted

Shortcut commands can uniquely identify key Input Gestures to be
deleted, while Key_gesture_type may not be unique, E.g For Application
shortcuts they all share the same key_gesture_type

Flag: com.android.systemui.extended_apps_shortcut_category
Test: customShortcutCategoriesRepositoryTest
Fix: 405058325
Change-Id: I891ab972456e0799700bc1bbaff29a4b9c6faed5