Remove widget education tip dialog

This change removes the widget education tip dialog, and the arrow
tip view. These are no longer needed now that taps are handled by
showing an add button.

Bug: 335318980
Test: `pm clear com.google.android.apps.nexuslauncher` and open widget
 picker
Flag: ACONFIG com.android.launcher3.enable_widget_tap_to_add NEXTFOOD
Change-Id: I9b24a41604880f5f94939c02b94f1a9f6a6c83d5