chore(android): bump source/target Compatibility to 21 #494

Job	Run time
setup	13s
release-dev-of-plugins (action-sheet)	26s
release-dev-of-plugins (app)	27s
release-dev-of-plugins (app-launcher)	26s
release-dev-of-plugins (browser)	24s
release-dev-of-plugins (camera)	27s
release-dev-of-plugins (clipboard)	24s
release-dev-of-plugins (device)	29s
release-dev-of-plugins (dialog)	23s
release-dev-of-plugins (filesystem)	25s
release-dev-of-plugins (geolocation)	24s
release-dev-of-plugins (haptics)	23s
release-dev-of-plugins (keyboard)	24s
release-dev-of-plugins (local-notifications)	30s
release-dev-of-plugins (network)	30s
release-dev-of-plugins (preferences)	24s
release-dev-of-plugins (push-notifications)	26s
release-dev-of-plugins (screen-orientation)	24s
release-dev-of-plugins (screen-reader)	25s
release-dev-of-plugins (share)	24s
release-dev-of-plugins (splash-screen)	25s
release-dev-of-plugins (status-bar)	31s
release-dev-of-plugins (text-zoom)	24s
release-dev-of-plugins (toast)	22s
	10m 0s

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