Excluded ClipboardFloatingActivity from App recents Screen

Summary

A small improvement in the clipboard workaround in Android X. The ClipboardFloatingActivity is now excluded from the Recents Screen. Since the ClipboardFloatingActivity is transparent and finishes quickly as soon as it sends the clipboard, this left its fingerprint on the recents screen.

Before:

After pressing Send Clipboard button in Android X notification, A blank activity is created in Recent Apps screen.

After:

This Blank Activity is not included in the Recents screen anymore.